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Biota of Freshwater Ecosystems 

Identification Manual No. 6 



Harley P. Brown 
Department of Zoology ] 
The University of Oklahoma 
730 Van Vleet Oval, Room 222 
Norman, Oklahoma 73069 



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April 1972 

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"Aquatic Dryopoid Beetles (Coleoptera) of the United States" 
is the sixth of a series of identification manuals for se- 
lected taxa of invertebrates occurring in freshwater systems. 
These documents, prepared by the Oceanography and Limnology 
Program, Smithsonian Institution for the Environmental Pro- 
tection Agency, will contribute toward improving the quality 
of the data upon which environmental decisions are based. 

Additional manuals will include, but not necessarily be lim- 
ited to, freshwater representatives of the following groups: 
branchiuran crustaceans [Argulus) , amphipod crustaceans 
(Gammaridae) , isopod crustaceans (Asellidae), decapod cray- 
fish crustaceans (Astacidae) , leeches (Hirudinea) , polychaete 
worms (Polychaeta) , freshwater planarians (Turbellaria) , and 
freshwater clams (Sphaeriacea) . 



An illustrated key is given for all known species of adult dryopoid 
beetles of the United States which have aquatic stages and might be 
useful as indicators of water quality. A key is also given to the 
genera of larvae. For each species the known habitat and range are 
given. Life histories are briefly outlined and methods for collection, 
preservation, storage and identification are suggested. Two new 
species, Optioservus ozarkensis Collier and Optioservus sandersoni 
Collier, are described. The genera included in the keys are: 
Chelonariidae- -Chelonarium; Elmidae--Tribe Larini: Lara^ Phanocevus; 
Tribe Elmini: AmpumixiSj Anayronyx ^ Atractetmis^ Cleptelmis^ CylloepuSj 
Dubiraphia, Elsianus, Gonietmis, Uetevelmis , Eetevlirrmius , Hexacytloepus ^ 
Maaronychus, Microoylloepus , NarpuSj NeooylloepuSj Neoelmis^ 
Optioservus 3 Ordobrevia^ Outirrmius^ Promoresia^ EhiselmiSj Stenelmis , 
Zaitzevia; Dryopidae- -ZPrzyopSj Hetichus, Pelonomusj Limnichidae-- 
Limnichinae: Lirrmichus, Lutroohus, Physemus; Cephalobyrrhinae: 
Throsoinus; Psephenidae--Eubriinae: AcneuSj DiaranopselaphuSj Ectopvia; 
Eubrianacinae: Eubri-anax; Psepheninae: Psephenus; Ptilodactylidae-- 
Andhyoteis, AnahytarsuSj Stenocolus. The bibliography includes 
selected useful references in addition to the literature cited. 

V References 

VII Index of Scientific Names 



I Introduction i 

Collecting 4 

Preservation and Storage 6 

Preparation and Equipment Needed for Identification 7 

II Species List and Ranges 13 

III Key to Aquatic Genera and Species of Adult Dryopoid Beetles 25 
of the United States 

IV Key to Genera of Aquatic and Semi-aquatic Dryopoid Beetle 55 
Larvae of the United States 


VI Glossary 73 


VI 1 



1-2 Adult elmid beetle: external features 8 

3-7 Adult elmid beetle: lateral and sectional views; mouthparts 8 
8-11 Adult elmid beetle: digestive, nervous, and reproductive systems9 

12-15 Elmid larva: external features, mouthparts 10 

16 Chelonarium leaontei adult 25 

17-18 Phanoaerus olavioomis, Lara avara adult 26 

19-21 Lara gehringi, L. avara avara^ L. a. amplipennis adult 27 

22-23 Maaronychus glabratus, Ancyronyx variegata adult 27 

24-25 Zaitzevia parvula, Ordobrevia nubifera adult 28 

26 Stenelmis crenata adult 29 

27-35 Tarsus, aedeagus of Stenelmis species 29 

36-41 Aedeagus of Stenelmis species 31 

42-48 Aedeagus of Stenelmis species 32 

49-54 Aedeagus of Stenelmis species 33 

55-56 Rhizelmis nigra adult 34 

57 Cleptelmis omata adult 35 

58-59 Atractelmis wawona adult 36 

60-61 Ampumixis dispar, Narpus oonaolor adult 36 

62-63 Dubiraphia quadrinotata^ Elsianus texanus adult 37 

64-65 Neoaylloepus boeseli^ Neoelmis oaesa adult 38 

66-67 Hexaoylloepus ferrugineuSj Eeterelmis vulnerata adult 39 

68-69 Cylloepus parkeri adult 40 

70-71 Microaylloepus pusillus, Oulimnius latiusaulus adult 41 

72-73 Gonielmis dietriohi, Promoresia elegans adult 42 

74-75 Heterlimnius aorpulentus, Optioservus ovalis adult 43 
76-82 Adult pronotum and elytron of Heterlimnius ^ Optioservus species 44 

83-89 Adult pronotum and elytron of Optioservus species 45 

90-91 Dryops arizonensis, Pelonomus obscurus adult 46 

92 Heliahus lithophilus adult 47 

93-98 Heliahus confluentuSi H. irmsi genitalia 47 

99-104 Heliahus produatus, H. lithophilus genitalia 48 

105-114 Aedeagus of Heliahus species 49 

115-116 Throsainus sahwartzi, Limniahus sp. adult 50 

117-118 Lutrochus luteuSy Aaneus quadrimaaulatus adult 52 

119-120 Eatopria nervosa, Diaranopselaphus sp. adult 52 

121-122 Eubrianax edwardsi, Psephenus texanus adult 53 

123-128 Aedeagus of Psephenus species 53 
129-131 Anahyateis velutina, Anahytarsus substriatus, Stenoaolus 

sautellaris adult 54 

132-133 Larvae of Chelonarium sp., Dryops sp. 55 

134-135 Larvae of Anahytarsus biaolor , Stenoaolus sautellaris? 56 

136-138 Larva of Lutroahus luteus 57 

139-142 Larvae of Lara avara, Phanoaerus alaviaomis 58 

143-146 Larvae of Dubiraphia sp., Narpus aonaolor 59 

147-150 Larvae of Cylloepus sp., C. montanus, Rhizelmis nigra 59 

151-155 Larvae of Anayronyx variegata, Eeterelmis vulnerata 60 

156-160 Larvae of Miaroaylloepus pusillus, Neoelmis sp. 61 


FIGURES - continued 

161-164 Larvae of Neoaylloepus boeselij Ordobrevia nubifera 61 

165-168 Larvae of Elsianus texanuSj Stenelmis sp. 62 

169-172 Larvae of Ampumixis dispar^ Cleptelmis sp. 63 

173-177 Larvae of Promoresia tardella, Optioservus sp. 63 

178-181 Larvae of Maoronyohus glabratus^ Zaitzevia parvula 64 

182-184 Larva of Gonietmis dietriohi 65 

185-188 Larvae of Heteretmis oorrpulentus , Oulirrmius latiusoulus 65 

189-190 Larva of Aaneus quadrimaaulatus 66 

191-194 Larvae of Diaranopselaphus sp., Eatopria nervosa 66 

195-198 Larvae of Eubrianax edwardsi, Psephenus texanus 66 



For practical purposes, one may consider any non-swimming aquatic 
beetle found in the United States to be a dryopoid. Although a few, 
such as Psephenus and LutroahuSj may be relatively conspicuous on rocks 
projecting from riffles, the majority are very small, inconspicuous, 
and slow-moving. Since the typical habitat of almost all dryopoids is 
in riffles, rapids, or comparable lotic situations, the common name 
"riffle beetle" is generally appropriate. Furthermore, since one 
author or another has applied this name to the dryopoids alone, the 
elmids alone, or the psephenids alone, while others have used it indis- 
criminately for all, it might as well be used for the entire group of 
aquatic dryopoids. 

The Superfamily Dryopoidea, in the Suborder Polyphaga, includes members 
(the Limnichidae) that are very close to the Byrrhoidea, and others 
that are closely allied to the Dascilloidea (most of the genera listed 
under Psephenidae and Ptilodactylidae are treated as members of the 
family Dascillidae by Amett (1963)). Crowson (1967) considers the 
Superfamily Dryopoidea as being comprised of the families Psephenidae, 
Eurypogonidae, Ptilodactylidae, Chelonariidae, Heteroceridae, 
Limnichidae, Dryopidae, and Elmidae. The Eurypogonidae and 
Heteroceridae are omitted from treatment here since none of our 
representatives of these families are known to be aquatic, although 
the heterocerids burrow in mud along the margins of streams, ponds, 
and lakes. By far the most promising as indicators of water quality 
are the elmids, but the psephenids, adults of Helichus (Dryopidae), 
and larvae of Lutroahus (Limnichidae) should also be useful for this 

Although somewhat detailed information concerning habitats of individual 
genera and species is presented in the species list, a few general facts 
concerning dryopoid life histories and ecology may be helpful. The 
elmids of the tribe Elmini are the most completely aquatic of all 
beetles. The eggs, so far as is known, are deposited on submerged 
rocks or wood, usually on the under side. Here the larvae develop, 
creeping about and feeding chiefly upon the algae which tend to encrust 
such substrates or upon decaying waterlogged wood. Respiration is 
accomplished by tufts of filamentous tracheal gills which are extruded 
from a caudal chamber. The gills may be retracted and the chamber 
closed by a trapdoor-like operculum. Mature larvae crawl out of the 
water and pupate in small cavities beneath loose bark or rocks close 
to the water's edge. Newly emerged adults of many species apparently 
fly at night, and are attracted to lights. Upon returning to the water, 
most individuals will never again emerge into the air, spending the 
rest of their lives (several years in some species) in the same habitat 
and utilizing the same food as the larvae. Their respiratory 

requirements are met through the use of a plastron (Thorpe, 1950; 
Thorpe and Crisp, 1949) . Various parts of the legs and body, especially 
on the ventral side, are covered with a hydrofuge tomentum or pile which 
maintains a film of air when the beetle is submerged. This film, which 
is in contact with the air reservoir beneath the elytra, provides 
adequate gaseous exchange in the well-aerated lotic situations occupied 
by the beetles. Small bubbles of oxygen photosynthetically produced by 
algae and other aquatic plants provide an additional source of oxygen 
and can be incorporated into the plastron. Since the gaseous film is 
essential to these beetles, it is not difficult to understand why they 
cannot tolerate excessive pollution by such wetting agents as soaps and 

Elmids of the tribe Larini are less thoroughly aquatic. The adults are 
essentially riparian, usually occurring at or just above the water line 
in rapids and creeping beneath the surface only for oviposition 
(presumably) . They take flight readily, often after dropping onto the 
water surface and being swept a short distance downstream. Otherwise, 
the life history is like that of the Elmini. 

Psephenus and Eubrianax^ in the family Psephenidae, exhibit a pattern 
very much like that of the Larini, except that the females may remain 
submerged for days as they go about their task of oviposition beneath 
rocks. Mature larvae (water pennies) crawl out and pupate beneath the 
larval carapace. Details are unknown for the members of the Eubriinae, 
but since the adults are found in shrubbery rather than at the water's 
edge, it is quite possible that the adults never enter the water, perhaps 
ovipositing on objects overhanging the stream as do such neuropterans as 
the sisyrids and dobsonflies. Pupation, at least in Eotopria, is 
comparable to that in Psephenus. 

In the family Limnichidae, Lutroohus has a life history that is also 
very much like that of the Larini, although the adults of some species 
may enter and remain under water for indefinite periods of time. 
Females insert their eggs in such substrates as travertine. The other 
genera of limnichids occurring within the United States are apparently 
not aquatic even as larvae. Their life histories are unknown. The 
adults are included in the key only because they may be taken near water 
(in fact, Lirrmichus commonly falls onto the water from trash lodged in 
the stream, and readily flies from the water surface as do LutrochuSj 
Psephenus, Phanoaerus, and Lara) . 

Chelonarium (Chelonariidae) is aquatic only in the larval stage, as are 
those members of the Ptilodactylidae listed here. Other ptilodactylids 
are not aquatic at all. 

Helichus, of the family Dryopidae, is unique among insects in that the 
adults are aquatic, behaving rather like elmids, whereas the larvae are 
terrestrial, inhabiting soil or decaying wood. The adults are not 
permanently bound to the water once they return to it. They probably 
emerge and fly at night, at least upon occasion. The females have sharp- 
tipped ovipositors with which they probably insert their eggs into 
appropriate materials. The larvae of Dryops and Pelonomus are also soil- 
dwellers, the adults being terrestrial or, at most, riparian. Dvyops 
frequents trash lodged in streams, but does not appear to enter the 


With a few notable exceptions, such as Psephenus and Eubrianax among the 
psephenids and such flightless elmids as Ancyronyx and Macronychus most 
of our dryopoid adults can be effectively collected with light traps and 
black lights. To be successful with this method, of course, one must use 
it when the adults have emerged from pupation. The best time will vary 
with locality, seasonal and weather conditions, and species. For example, 
in Oklahoma in an average year, Ectopria may be taken in abundance at 
lights on humid nights in very late May and early June; at other times 
they are unlikely to be taken. Specimens collected at lights are ideal 
for taxonomic purposes, at least in that they are not encrusted with 
mineral deposits or bedecked with epizoic organisms such as diatoms and 

Perhaps the most useful general method of collecting the aquatic larvae 
and adults that inhabit gravelly and rocky riffles is to hold a delta net 
against the bottom in such a way as to catch the organisms dislodged 
while turning over rocks just upstream from the net, or vigorously 
stirring up the gravel by hand, heel, alpenstock, or whatever is at hand. 
(A small rake serves rather well.) This is probably the best method for 
most of the elmids and Helichus. 

Nets are not effective for most of the species that cling tightly to 
submerged wood or plants. Usually one must remove logs or sticks from 
the water, turn them over, let them drain briefly, then laboriously pick 
off the specimens as they creep downward. The same can be done with 
rocks, and this is often very productive. Or one can place the stick or 
rock over a white pan or old sheet and let the specimens collect them- 
selves (they will accompanied, of course, by caddis worms and most of 
their other former neighbors) . These techniques are best for such genera 
as Ancyronyx 3 Macronychus, Gonietmis, and Heterelmis. Most larval 
psephenids must be picked off the rocks. 

For species that inhabit such things as submerged plants or roots, a 
Berlese funnel may be the most productive collecting device. Quantities 
of the plant materials can be transported in large plastic bags to the 
laboratory and placed in the funnel beneath some source of heat (light 
bulbs are adequate) . A screen of hardware cloth prevents the larger 
objects from falling below, but the beetles will drop into a waiting 
receptacle of preservative. This is a good method for getting large 
numbers of Dubiraphia. 

Disturbing trash (leaves, etc.) lodged on sticks or rocks in streams 
while holding a net downstream to catch the dislodged specimens being 
swept down afloat is effective for collecting Dryops, Limniohus, 
Phanocerus, Psephenus, and Lutrochus. For dislodged specimens swept 
downstream underwater, it is good for getting Helichus, Heterelmis, and 
Microcy I loepus . 

For agile fliers such as Psephenus and Lutrochus on rocks protruding 
from rapids or riffles, a net or plastic bag may be useful for catching 
the specimens that tumble onto the water to be swept downstream briefly 
before taking flight, but many specimens can be taken by aspirator or by 
hand (it is best to wet your fingers first) . Approach the beetle care- 
fully, without sudden movements, and pin it down lightly with a fore- 
finger. The thumb and middle finger can then be used to grasp it. 

Sweeping foliage of trees and shrubs near streams may yield adults of 
the Eubriinae, Chelonariidae, and Ptilodactylidae. This is not very 
efficient, but no better method is known for collecting some of these. 


For routine collecting, a supply of 4-drara vials almost full of 80% 
ethyl alcohol is handy. Fine-tipped forceps, preferably of the curved 
type, are indispensable. If not young and near-sighted, the collector 
should have either magnifying glasses or glasses enabling him to read 
fine print. 

For ordinary purposes, 70-80% ethyl alcohol is satisfactory for killing, 
transport, and storage of both larvae and adults. If one anticipates 
detailed dissection of internal parts, it may be better to preserve 
initially in Pampl's fluid, which contains acetic acid for rapid pene- 
tration. Specimens should be removed from Pampl's fluid to 70-80% 
alcohol for storage. Whether the insects have been killed in alcohol or 
in Pampl's fluid and then transferred to alcohol, if is best to change 
the alcohol after a few days. It is also sometimes desirable to add 
about 5% glycerol to the alcohol in which specimens are stored. This 
serves a dual function: it helps keep the appendages flexible and, 
should the cap not prove airtight, prevents complete drying of the 
specimen if all the alcohol evaporates. 

Pampl's Fluid 

Glacial acetic acid 4 ml 

Distilled water 30 ml 

Formalin (40% formaldehyde) 6 ml 

95% ethyl alcohol 15 ml 

A common and sensible museum storage method for specimens preserved in 
alcohol is to place the specimens in vials, along with appropriate data 
and alcohol, to plug with cotton or cotton wool, then to place upside 
down for storage in a larger jar half filled with alcohol. Cheap shell 
vials are satisfactory for this, and many can be kept in a single jar. 
If vials are to be stored instead in narrow trays, it is probably best 
to use patent lip vials with rubber stoppers. Cork stoppers are 
totally unreliable, and a discouraging percentage of screw-cap vials 
allow evaporation of the alcohol because of imperfections of either the 
lip or the cap liner. 

For standard dry preservation of adults in Schmitt boxes or cabinet 
drawers, virtually all of our dryopoid beetles are small enough for the 
use of points. In fact, most are so small that they cannot be pinned 
otherwise, even with minuten nadeln. 


For identification of genera or species, a stereoscopic microscope, spot 
lamp, forceps, and fine needles are necessities. Disposable hypodermic 
syringe needles (e.g.. No. 26) attached to any convenient handle make 
excellent micro-scalpels. All dissections and most examination of 
material, particularly of larvae, should be done with the specimen 
immersed in water or alcohol. For specific determination in some genera, 
such as Stenelmis^ it is necessary to extract the male genitalia and to 
mount them on a microscope slide for examination under a compound micro- 
scope. Glycerol (glycerine) is satisfactory for temporary microscopic 
preparations. Hoyer's mounting medium (obtainable from Ward's Natural 
Science Establishment, Rochester, New York) is quite convenient for 
temporary and semi-permanent mounts. Canada balsam is perhaps best for 
permanent mounts, though it is time-consuming, since specimens must be 
completely dehydrated through a graded series of alcohol concentrations, 
then saturated with a suitable solvent such as xylol or toluol, before 
placing in the balsam. 

Most specimens as brought in from streams are well covered with either 
mineral deposits (sometimes far exceeding the weight of the insect) or 
epizoic organisms such as diatoms and peritrich ciliate protozoa. A 
sonic cleaning tank is helpful, but removes only the rather loosely- 
adhering "dirt". A closely-trimmed camel 's-hair brush is also quite 
useful in cleaning specimens, but often only breaking of the mineral 
"armor" with forceps or scraping with a needle can reveal the surface 
of the insect. Care must be exercised in such scraping, for it is easy 
to scrape through the cuticle and artificially produce misleading mark- 
ings or coloration. 

When required for specific determination, genitalia may be removed in 
at least two ways: (1) using a stereoscopic microscope to observe, hold 
the specimen between the thumb and forefinger of one hand; with fine- 
tipped watchmaker's forceps in the other hand, insert the tips between 
the last abdominal stemite and elytral apex (Figs 1, 2); grasp and ex- 
tract whatever you can. With a little experience, one can usually 
remove the genitalia by this means. The other method is usually more 
destructive to the specimen. (2) Remove either the abdomen (it can 
often be glued back into place if necessary) or the elytra. This 
exposes the soft dorsal tergites of the abdomen, through which an 
incision can be made - or the whole dorsum torn off- to expose the 
underlying visceral organs. Usually the only prominent sclerotized 
structure in the abdomen of the male is the genital complex. This can 
be removed and teased apart in appropriate fashion. As a rule, the 
soft enclosing tissues must be torn away, along with the penial spicules 
(Fig. 10) in order to expose the genitalia. Further cleaning and clear- 
ing can be accomplished by placing the genitalia in a hot aqueous 
solution of strong potassium hydroxide for about 15 minutes. After 
rinsing in distilled water, then 70% alcohol, the specimen may be 

hrnd wing showing venation 
(as unfolded for fitght) 

apical segment 
of antenna 

vertex of head 

apical angle of 

crenate lateral 

sublateral carina 


umbone. humerus, or 

humeral angle 
sublateral cannae 

of elytron 

punctae ot first 

sutural interval 

serrate lateral 
marg rn 

pleural spiracle 


edge of 4th 

apex of elytron 

Fig. 1. Dorsal features of adult elmid beetle. 

first or basal segment of 





maxillary palp 

labial palp 



prosternal episternum 

(prosternal epimeron) 

prosternal process 

mesosternal episternum 

mesosternal epimeron 


met a sternal episternum 

epipleuron (=elytral 

metacoxal cavity 




3rd abdominal sternite 

tibia with tomentum 

produced margin of 
Gtermte which clasps 
epipleuron of elytron 

1st segment of tarsus 

Fig. 2. Ventral features of adult elmid beetle. 

pronolal hypomeron 

lateral margin of elytron 
sublateral carinae 



carina ol elytron 

tiind wing 


abdonninal tergite 

serrate margin 

. (tubercle) 


spiracle (in pleuron ) 

malpighian tubule 

abdominal sternite 

ventral nerve cord 

apical tooth 

lateral lobe 

Figs 3-7 Adult elmid beetle: 3- lateral aspect; 4- diagrammatic 
cross section through abdomen; 5- mandible of Heterelmis 6- maxilla, 
right side, ventral aspect, of Neocylloepus; 7- labium, ventral as- 
pect, of Neoaylloepus. 

mounted in Hoyer's medium and examined promptly. By jiggling of the 
cover glass with a needle, one can usually get the specimen into the 
necessary position for observation (at times a dorsal view is needed, 
at other times, a lateral or ventral view may be desired). Since 
Hoyer's medium is soluble in either alcohol or water, the specimens may 
be readily removed even after months on the slide. 

A formidable vocabulary has arisen for the description and classification 
of beetles. This is not surprising, in view of the fact that they repre- 
sent the largest order of plants or animals. Nor is it surprising that 
some terms have been used in diverse ways or that a number of different 
terms have been used for a particular structure. Figures 1-15 should 
assist the reader not only in making use of the following keys but also 
in understanding the more detailed references he may consult. These are 
diagrams or simplified figures of representative dryopoid beetles, 
illustrating the major morphological features and the terms most commonly 
applied to them. The figures should be useful even though some of the 
terms are not employed in the keys. It will be worthwhile to study Figs 
1-15 with care before attempting to use the keys. These figures serve 
as an illustrated glossary, though a standard form of glossary is appen- 
ded (p. 73). 

lore gut (stomodeum) 


mid gut (mesenteron) 

malpighian tubule 

lunction ot mid gut 
and hind gut 

hind gut (proctodeum) 


subesophageal ganglion 
1st thoracic ganglion 

1st abdominal ganglion 

fused 5th to 8th 
abdominal ganglia 

sperm tube or 
lobe of testis 

was etterens 

vas detereni 

lateral accessory 

median lateral 
accessory gland 

seminal vesicle 
ejaculatory duct 

penial spicule 

basal piece or 

paramere or 
lateral lobe 

penis or median lobe 
ostium o1 interna! sac 

aedeagus or 
male genitalia 

egg tube or ovanole 


lateral oviduct 
median oviduct 
spermathecal duct 
bursa copulatrii 
vag ina 
bacuium (valviler) 

hemisternite (comte) 

stylus (may protrude 


Figs 8-11 Adult elmid beetle: 8- dorsal aspect of digestive tract 
of Neoaylloepus; 9- central nervous system of Neoaylloepus; 

10- male reproductive system, dorsal aspect, of Neoaylloepus; 

11- female reproductive system, dorsal aspect. 

If the reader is unfamiliar with insects, he would be well advised to 
consult a general textbook of entomology. For general coverage of 
aquatic insects, two books are outstanding. The sections of these books 
dealing with the Coleoptera are cited in the bibliography: Leech and 
Chandler (1956), and Leech and Sanderson (1959). Both were extremely 
helpful to me in the preparation of the keys which follow, as was the 
work of Sanderson (1953-54) . 


Among the beetles treated in these keys are groups of species which 
need revision. In the absence of described characters which clearly 
distinguish species, geographical location is used in the key so that 
identification may be made according to published accounts. 

Figs 12-15 Elmid larva (Neoaylloepus) : 12- dorsal aspect; 

13- ventral aspect; 14- left maxilla, ventral aspect; 15- labium, 

ventral aspect. 



In this section two new species, Optiosevvus ozarkensis and 0. 
sandersoni, are described by Joe Edward Collier. He submitted his Ph. D. 
thesis (Collier, 1969) to the Graduate School of the University of 
Minnesota in August, 1969 but died of cancer that same month. His Major 
Professor, Dr. Edwin F. Cook, has authorized publication here of 
Collier's descriptions as a means of validating Collier's authorship of 
these two species. The descriptions presented here are taken from 
Collier's thesis and authorship is to be ascribed solely to Joe Edward 

Family CHELONARIIDAE (Lacordaire, 1854) 

Genus Chelonarium Fabricius, 1801 

Chelonariim leaontei Thomson, 1867. Though probably not really aquatic, 
larvae in damp moss may be washed into streams; adults usually on 
vegetation or taken at lights in southeastern states from Florida 
to North Carolina, Tennessee, and Alabama. 

Family ELMIDAE (ELMINTHIDAE) (Westwood, 1838) 

Tribe Larini 

Genus Lara LeConte, 1852 

Lara avara avara LeConte, 1852. Rapid, clear mountain and foothill 

streams from British Columbia to southern California and eastward 
through Idaho and Utah to Wyoming and Colorado. Larvae on sub- 
merged wood and debris; adults usually on logs just above churning 
or rushing water, either beneath or on the downstream side of the 

Lara avara amplipennis Darlington, 1929. Habitat as above from 
British Coliombia and Washington. 

Lara gehringi Darlington, 1929. Habitat as for L. avara from 
Washington south to central California. 

Genus Phanoaerus Sharp, 1882 

Phanoaerus olavioomis Sharp, 1882. Rapids and riffles from Central 

America and Mexico northward to Val Verde Co., Texas (known in the 
United States from Devil's River and San Felipe Creek in Del Rio). 
Larvae typically on submerged plant material; adults just above or 
just below water line on objects protruding from water in rapids or 
small falls. 


Tribe Elmini 

Genus Ampwnixis Sanderson, 1954 

Ampimixis dispar (Fall, 1925). In sandy and gravelly bottoms of rapid, 
clear, cool or cold streams in foothills and mountains from 
Washington south to California. 

Genus Anoyronyx Erichson, 1847 

Anoyronyx variegata (Germar, 1824) . On submerged wood or trash (larvae 
may be under decaying bark) in streams throughout the eastern 
states from Maine to Florida, westward to Wisconsin and the 
eastern portions of Kansas, Oklahoma, and Texas. Sensitive to 
sewage and industrial wastes. 

Genus Atractelmis Chandler, 1954 

Atractelmis wawona Chandler, 1954. Rare in riffles of rapid, clear 
mountain streams in California at elevations from 2,000 to 5,000 
feet (actually reported from only two localities - the South Fork 
of the Merced River near Wawona in Yoseraite National Park and 
Middle Fork of Cottonwood Creek, Shasta County) . 

Genus Cleptelmis Sanderson, 1954 

Cleptelmis addenda (Fall, 1907). On roots and moss or rocks and gravel 
in rapid, cold mountain or foothill streams from California and 
southeast Oregon to New Mexico and South Dakota. 

Cleptelmis ovnata (Schaeffer, 1911). On roots, moss, rocks, and gravel 
in rapid mountain or foothill streams from central California to 
British Columbia and eastward to Arizona, Colorado and Montana. 

Genus Cylloepus Erichson, 1847 

Cylloepus abnormis (Horn, 1870) . Beneath rocks and in sandy gravel in 
riffles of creeks and rivers throughout Mexico, but extending into 
Arizona (San Pedro River) and Texas (Limpia Creek in the Davis 
Mountains, small stream near Camp Wood). Common in Mexico (known 
as Cylloepus sexualis Hinton) but rare in the United States. 

Cylloepus parkevi Sanderson, 1953. Known only from small, rocky streams 
in Bloody Basin, Yavapai Co., Arizona. 

Genus Dubiraphia Sanderson, 1954 
(This genus is currently under revision by Dr. William Hilsenhoff. 
Some of these species may be combined. Others will be added.) 

Dubiraphia bivittata (LeConte, 1852) . On submerged roots, aquatic 
plants, or other plant material in streams and lakes of eastern 
states, and upper Mississippi River drainage. 


Dubiraphia brunnescens (Fall, 1925). Among submerged willow roots along 
rocky, wave-washed shore of Clear Lake, Lake Co., California. 

Dubiraphia giulianii (Van Dyke, 1949). Described from vegetation and 

rocks in the slow part of Russian River, California. Also reported 
from eastern Oregon and southern Idaho. 

Dubiraphia quadrinotata (Say, 1825). On submerged roots, aquatic plants, 
or other plant material (including rocks encrusted with algae) in 
streams, ponds, and lakes throughout the eastern and central states 
where it is often abundant, and in scattered streams westward to 
New Mexico, Utah, and Idaho. Sensitive to chlorides; occurs in 
recovery zone below sewage treatment plants. 

Dubiraphia vittata (Melsheimer, 1844). As above. 

Genus Elsianus Sharp, 1882 
(This genus is currently under revision by Dr. Howard Hinton.) 

Elsianus moestus (Horn, 1870). Beneath rocks in Arizona streams. 
Elsianus shoemakei Brown, 1971. In gravel or beneath rocks in San 

Felipe Creek in Del Rio, Texas and the upper Rio Salado in 

Coahuila, Mexico. 
Elsianus texanus Schaeffer, 1911. In gravel or under rocks in streams 

with a high calcium content from Austin, Texas to southeastern New 

Mexico and southward into Mexico. 

Genus Gonielmis Sanderson, 1954 

Gonielmis dietriohi (Musgrave, 1933). On submerged wood and roots in 
sandy streams from eastern Tennessee, Georgia, and Florida to 
Mississippi. Tolerant of moderate organic enrichment, turbidity, 
and siltation, but sensitive to paper mill effluent. 

Genus Heterelmis Sharp, 1882 
(A new species is being described from the Santa Rita Mountains of 

Eeterelmis glabra (Horn, 1870) . On submerged wood and trash and under 
stones, especially in lowland streams from southern Nevada, 
through Arizona, much of Mexico, and in the Rio Grande River along 
the Texas border. 

Eeterelmis obesa Sharp, 1882. On submerged wood and under stones in 

cold, fast streams of Arizona and New Mexico, especially at higher 

Eeterelmis vulnerata (LeConte, 1874) . On submerged wood and debris 
and under rocks in streams of Oklahoma and Texas. 

Genus Eeterlimnius Hinton, 1935 

Eeterlimnius oorpulentus (LeConte, 1874). In gravel and under rocks 
in rapid mountain streams from New Mexico to California and 
northward to South Dakota, Montana, and British Columbia. 


Heterl-tmnius koehelei (Martin, 1927) . In rapid mountain streams from 
northern California to British Columbia. 

Genus Hexaoylloepus Hinton, 1940 

Hexaoylloepus ferrugineus (Horn, 1870). On travertine, under rocks, in 
gravel, and sometimes on wood, chiefly in riffles of streams with a 
calcium content from Mexico through central Texas into the 
Arbuckle Mountain region of south central Oklahoma and into south- 
eastern New Mexico. 

Genus Maaronyohus Muller, 1806 

Macronyohus glahvatus Say, 1825. On submerged wood and debris in 

streams of the eastern and central states from Florida to Maine and 
eastern Texas and Oklahoma to Wisconsin. Sensitive to sewage and 
many industrial wastes, such as those from plating, textile, and 
viscose rayon plants. 

Genus Micvooylloepus Hinton, 1935 
(Other species will soon be described, including one from springs 
in Death Valley, California.) 

M-iovocylloepus browni (Hatch, 1938) . Warm spring in Montana. 

Miaroaylloepus moccpus La Rivers, 1949. Warm springs in southeastern 

Micvooylloepus moccpus fraxinus La Rivers, 1949. Warm springs in 
southeastern Nevada. 

Micvooylloepus pusillus (LeConte, 1852) . Versatile and common on sub- 
merged wood and debris, under rocks, or in gravel of streams from 
Mexico east to Florida, west to California, and north to Oregon, 
Idaho, Wyoming, South Dakota, Missouri, Tennessee, and among the 
eastern states to Maine. Tolerant of siltation and turbidity, but 
sensitive to sewage and such industrial wastes as those from rayon 
plants and plating mills. 

Micvooylloepus pusillus ccptus (Musgrave, 1933) . Northern Florida to 

Micvooylloepus pusillus pusillus (LeConte, 1852) . Virginia to New 

Micvooylloepus pusillus lodingi (Musgrave, 1933) . Southeastern (Gulf) 
coastal plain. 

Micvooylloepus pusillus pevditus (Musgrave, 1933) . Peninsular Florida. 

Micvooylloepus pusillus similis (Horn, 1870). West of the Rocky Mountains, 

Micvooylloepus thermavum (Darlington, 1928) . Warm springs in north- 
western Nevada. 

Genus Navpus Casey, 1893 
(A new species will soon be described.) 

Navpus angustus Casey, 1893. In gravelly or rocky rapids of clear 
streams in the coastal range of California. 


Narpus arizonicus (Brown, 1930). In rapid streams of the White Moun- 
tains of eastern Arizona. (This may be but a variant of N. concotor') 

Narpus concotor (LeConte, 1881). In clear, rapid, cool or cold streams 
of western states from New Mexico to California and north into 

Genus Neocyltoepus Brown, 1970 

Neooylloepus boeseli Brown, 1970. In gravel and rocks of rapids in 

Devil's River northwest of Del Rio, Texas and West Clear Creek east 
of Camp Verde, Arizona. 

Genus Eeoelmis Musgrave, 1935 

Neoelmis oaesa (LeConte, 1874). In gravel and under rocks in riffles of 
clear streams with a high calcium content in south-central and south- 
western Texas, the Arbuckle Mountain region of south-central Oklahoma 
and southeastern New Mexico. 

Genus Optioservus Sanderson, 1954 

Optioservus ampliatus (Fall, 1925). In riffles of gravelly or rocky, 

clear streams from Virginia northward into Canada, Relatively 

tolerant of sewage and chlorides. 
Optioservus canus Chandler, 1954. Known only from Chalone Creek in 

Pinnacles National Monument of west central California. 
Optioservus cryophilus (Musgrave, 1932) . On moss-covered stones in 

fast, spring-fed brooks of the Great Smoky Mountains. 
Optioservus divergens (LeConte, 1874) . In gravelly or rocky riffles of 

clear streams from New Mexico to California and north into Canada. 
Optioservus fastiditus (LeConte, 1850) . In gravelly or rocky riffles or 

on wood in fast streams in upper New York and from Michigan to 

Optioservus immunis (Fall, 1925). In gravelly or rocky streams of 

Connecticut, New Jersey, and Pennsylvania. (Records from Georgia 

and Tennessee may represent 0. cryophilus, which greatly resembles 

0. immunis) . 
Optioservus ovalis (LeConte, 1863) . In gravel or among moss-covered 

stones in clear, riffly streams from North Carolina north to Vermont 

and west to Alabama and Ohio. 

Optioservus ozarkensis Collier, n. sp. (see page 13) (Fig. 83) 

Type locality: Holotype, male. Roaring River State Park, Cassville, 
Missouri. Collected 30 December 1968 by Joe E. Collier. 

Location of Type: Holotype, male. Department of Entomology, Fisheries, 
and Wildlife, University of Minnesota; four paratypes. Snow 
Entomological Museum, University of Kansas, Lawrence, Kansas; ten 
paratypes will be deposited in California Academy of Sciences 


DIAGNOSIS: This species resembles Optioservus trivittatus (Fig. 81) in 
appearance but is larger and has very different markings. 

DESCRIPTION: Holotype male: Length 2.3 mm, width 1.2 mm; head and 

thorax shiny black, scutellum ochreous; elytra fuscous brown with 
yellow-orange markings; venter fuscous brown; entire body covered 
with short depressed hairs which are much more abundant on ventral 
surface . 

Head : Black; maxillary palpi four- segmented; antennae testaceous, 
eleven- segmented, length 0.5 mm, segment eleven twice as long as 
nine or ten, segment three four-fifths as long as eleven, segments 
one and two almost as wide as long. 

Pronotum : Length 0.6 mm, width 0.8 mm; sides arcuately convergent 
anteriorly, disc covered with very shallow punctuations, basal sub- 
lateral carinae 0.2 mm long extending anteriorly. 

Elytra : (Fig. 83) Wider than thorax, widest near middle; length 1.7 
mm, width 1.2 mm; strial punctures shallow, separated by distance 
greater than their width; humeral spot reaching seventh stria and 
extending to suture, then posteriorly two-thirds of way along 
elytron; second elongate spot extending from just below middle 
almost to apex of elytron. 

Venter : Covered with heavy hydrofuge pubescence, especially on ab- 
domen. Legs ochreous yellow throughout entire length. 


SPECIMENS EXAMINED: Holotype (male), four paratypes from Roaring River 
State Park, Missouri, and ten paratypes from Big Spring State Park, 
Missouri, taken June 1954, July 1954 and December 1968. 

Optioservus pecosensis (Fall, 1907). In clear, cool or cold, gravelly 
or rocky streams from New Mexico to California and north to Wyoming 
and Washington (according to Collier) . (May well be confused with 
0. divergens . ) 

Optioservus quadrimaculatus (Horn, 1870). In gravelly or rocky riffles 
from Colorado west to California and North to Montana and British 

Optioservus sandevsoni Collier, n. sp. {see page 13) (Fig. 82) 

Type locality: Washington Co., Arkansas, 16 June 1962; Lot No. 193. 

Location of type: Holotype, male, and three paratypes, will be deposited 
in Illinois Natural History Survey Collection. 

DIAGNOSIS: This species resembles Optioservus trivittatus (Fig. 81) and 
Optioservus ozarkensis (Fig. 83), but may be separated from all 
other Optioservus by the two spots and one sutural vitta on each 
elytron (Fig. 82). This type of marking has not been found on any 
other Optioservus. 

DESCRIPTION: Holotype male: Length 2.6 mm, width 1.3 mm; head and 

thorax black with yellowish-grey pubescence; scutellum yellowish- 
orange; elytron dark red-brown with yellowish-orange spots and 
sutural vitta, striae not deeply punctured on elytron. 
Head : Black; clypeus covered with greyish pubescence; maxillary 


palpi four-segmented, red-brown in color; labial palpi red-brown, 

three-segmented; antennae eleven-segmented, reddish-yellow, first 

three segments equal to length of next six. 

Pronotum : Black; sparse yellowish pubescence; very shallow 

punctures; sides very slightly converging toward apex from base, 

carinae extending from base nearly to middle, parallel to lateral 

margin of thorax. 

Elytra : (Fig. 82) Dark red-brown; each elytron containing one 

rounded humeral spot and one elongated apical spot with sutural 

vitta extending from scutellum to apical third of elytra; spots 

and vitta yellow-orange in color. 

Venter : Epipleuron and most of thorax and abdomen covered with 

short grey pubescence; legs reddish-yellow; most of underside just 

slightly darker than legs in color. 

Female: As for male. 

DISTRIBUTION: Arkansas and Oklahoma. 

SPECIMENS EXAMINED: Holotype (male), three paratypes from Washington 
Co., Arkansas, four paratypes from Ottawa Co., Oklahoma, taken in 
June 1930 and 1962. 

Optioservus seriatus (LeConte, 1874) . In gravelly or rocky riffles from 

north coastal California to British Columbia and in scattered 
localities in New Mexico, Utah, and Idaho. 

Optioservus trivittatus (Brown, 1930). In gravel, under rocks, or on 

wood in fast streams from the Great Smoky Mountains north to 

Vermont and Quebec, and in Michigan and Wisconsin. Relatively 
tolerant of sewage and chlorides. 

Genus Ovdobrevia Sanderson, 1953 

Ordobrevia nubifera (Fall, 1901). In gravel and under rocks of foot- 
hill streams from California to Washington. 

Genus Oulirrmius Des Gozis, 1886 

Oulirrtni-us latiusculus (LeConte, 1866) . In gravel or under rocks in 
riffles of clear streams (often very small brooks) from Alabama, 
eastern Tennessee, and South Carolina northeast to Canada, ranging 
from cool lowland streams to elevations higher than any of the other 
local elmids. 

Genus Promoresia Sanderson, 1954 

Pvomoresia elegccns (LeConte, 1852) . In gravel and under rocks in 

riffles of cool streams from the Great Smoky Mountains northeast to 
lower New England. Promoresia is unusual among members of its sub- 
family in that it often takes flight when removed from the water, 
a feature which is characteristic of the Larinae and of Limnichidae 
and Psephenidae. 

Promoresia tardella (Fall, 1925). In gravel and among moss and rocks of 
riffles of cool streams in the Great Smoky Mountains and in New 
England and eastern Canada. 


Genus Rhizelmis Chandler, 1954 

Rhizelmis nigra Chandler, 1954. In fast, cool, shaded streams from 2,000 
to 5,000 feet elevation in central and northern California. 

Genus Stenelmis Dufour, 1835 
(Several new species will soon be described; surprising records 
have appeared from southern Idaho and from eastern Oregon.) 

Stenelmis antennalis Sanderson, 1938. Commonly on submerged wood and 

debris (especially under loose bark) in sandy southeastern streams 

from Mississippi to Florida. 
Stenelmis beameri Sanderson, 1938. Cool, clear Ozark streams of 

Arkansas, Missouri, and Oklahoma; also reported from central and 

eastern Tennessee. 
Stenelmis hiaarinata LeConte, 1852. Gravelly or rocky streams from 

Vermont to South Carolina, west to Wisconsin and Texas and south- 
eastern New Mexico. 
Stenelmis aalida calida Chandler, 1949. In warm spring pool in southern 

Stenelmis aalida moapa La Rivers, 1949. In warm streams of southern 

Stenelmis conoinna Sanderson, 1938. In eastern streams from North 

Carolina to Quebec. 
Stenelmis aonvexula Sanderson, 1938. In sandy, gravelly or rocky streams, 

often on submerged wood, from northwestern Florida west to Texas 

and southern Oklahoma. 
Stenelmis arenata (Say, 1824) . In stream riffles from Alabama and 

northwestern Florida northeastward to New Brunswick and westward to 

Texas and Wisconsin. Tolerant of chlorides but sensitive to sew- 
age and phosphate wastes. 
Stenelmis decorata Sanderson, 1938. In streams from South Carolina to 

Maryland and west to Kansas and Wisconsin. Tolerant of sewage and 

phosphate wastes. 
Stenelmis douglasensis Sanderson, 1938. On wood in lakes in Michigan 

and Wisconsin. 
Stenelmis exigua Sanderson, 1938. In clear streams of western Arkansas 

and eastern Oklahoma. 
Stenelmis exilis Sanderson, 1938. In clear streams of western Arkansas 

and eastern Oklahoma. 
Stenelmis fuscata Blatchley, 1925. From the sandy streams of northern 

and central Florida to wave-washed lake margins in Lake Co. to 

drainage canals of the Everglades. 
Stenelmis gvossa Sanderson, 1938. In sandy streams from Mississippi to 

Texas and Arkansas, usually beneath sunken logs. 
Stenelmis humerosa Motschulsky, 1859. In streams from Massachusetts 

south to South Carolina and Tennessee. 
Stenelmis hungerfordi Sanderson, 1938. Under rocks in fast streams (with 

high calcium content) from northwestern Florida to South Carolina. 
Stenelmis knobeli Sanderson, 1938. In streams of southwestern Arkansas. 
Stenelmis lateralis Sanderson, 1938. In streams from Virginia and 

Pennsylvania to northeastern Oklahoma. 


Stenetmis mavkeli- Motschulsky, 1854. In streams from Massachusetts 

south to Tennessee and west to Wisconsin and Oklahoma. 
Stenetmis mera Sanderson, 1938. In streams from Quebec south to North 

Carolina and west to Wisconsin and Arkansas. 
Stenetmis mirabitis Sanderson, 1938. In eastern streams from 

Connecticut to South Carolina. 
Stenetmis musgravei Sanderson, 1938. In streams from New York to 

South Carolina and west to Wisconsin and Texas. 
Stenetmis parva Sanderson, 1938. In streams in southeastern Oklahoma 

and eastern Texas. 
Stenetmis quadrdmacutata Horn, 1870. In lakes and marl bogs from 

Quebec to Maryland and west to Indiana and Michigan. 
Stenetmis sandersoni Musgrave, 1940. In streams from Ontario and 

West Virginia to northeastern Oklahoma. 
Stenetmis sextineata Sanderson, 1938. In streams from Tennessee and 

Kentucky to Indiana, Kansas, Oklahoma, and Texas. Tolerant of 

moderate pollution by sewage, phosphate, and a variety of wastes. 
Stenetmis sinuata LeConte, 1852. In sandy streams from Florida to South 

Carolina and west to Mississippi. 
Stenetmis vittipennis Zimmerman, 1869. In streams from Quebec to South 

Carolina and west to North Dakota and Kansas. 

Genus Zaitzevia Champion, 1923 

Zaitzevia parvuta (Horn, 1870) . Usually in gravel or under rocks in 
fast mountain streams of western states from New Mexico to 
California and north to South Dakota, Montana, and British Columbia. 

Zaitzevia thermae (Hatch, 1938) . In warm springs of Montana. (Perhaps 
this is only an ecological variant of Zaitzevia parvuta.) 

Family DRYOPIDAE (Erichson, 1847) 

Genus Dry ops Olivier, 1791 

Dryops arizonensis Schaeffer, 1905. Usually just above the water line 
in debris caught on sticks or rocks in stream riffles (or taken at 
lights) in central and southern Arizona. 

In addition to this known distribution of Dryops in the United States, 
we may expect the genus to occur in southeastern California, in New 
Mexico, and in Texas along the Rio Grande (I have taken it just over the 
border in Mexico) . Furthermore Dryops viennensis (Heer, 1841) , an acci- 
dentally imported species from Europe, has become established in Quebec, 
and is to be expected in Maine. 

Genus Hetiohus Erichson, 1847 

Eetiohus basatis LeConte, 1852. Beneath rocks near the shore in streams 
from Georgia to Massachusetts and west to Texas, Kansas, and Ohio. 


Helichus confluentus Hinton, 1935. On debris and beneath rocks usually 
in upland or mountain streams of western Texas, New Mexico, and 
Arizona, but with a disjunct population in the mountains of northern 
Georgia (Rabun Bald) . 

Helichus fastigiatus (Say, 1824) . Under rocks in streams from Florida 
to Maine and Canada, west to Illinois, eastern Kansas and Oklahoma. 

Helichus immsi Hinton, 1937. On debris and under rocks in streams from 
western Texas to California, often abundant. 

Helichus lithophilus (Germar, 1824) . Under stones or on submerged wood 
in streams from Florida to Canada and west to Wisconsin, Iowa, cen- 
tral Oklahoma and Texas. 

Helichus productus LeConte, 1852. On debris and under rocks in valley 
and foothill streams of central and southern California. 

Helichus striatus LeConte, 1852. On debris and under rocks in cool 
streams from South Carolina to Quebec, west to California and 
British Columbia. 

Helichus striatus foveatus LeConte, 1852. On debris and under rocks in 
western streams up to elevations well above 8,000 feet, from 
Arizona and Califomi? to British Columbia. 

Helichus suturalis LeConte, 1852. On debris and under rocks in all sorts 
of streams from warm, muddy, lowland rivers to mountain brooks well 
above 8,000 feet from central Oklahoma and Texas west to Utah and 
California and south to Guatemala; often abundant and frequently the 
only dryopoid in lowland southwestern streams. 

Helichus triangularis Musgrave, 1935. On debris and under rocks in small 
mountain streams from the Chisos and Davis Mountains of Texas to the 
Chiricahua and Huachuca Mountains of Arizona. 

Genus Pelonomus Erichson, 1847 

Pelonomus obscurus LeConte, 1852. Not a "riffle" beetle. On aquatic 
plants and debris in swamps and ponds (though most often taken at 
lights) from Florida to Texas and north to Illinois. 

Family LIMNICHIDAE (Thomson, 1860) 

Subfamily Limnichinae 

Genus Limnichus Latreille, 1829 
Many species have been described, but none are known to be aquatic, 
although the adults may be found in damp places such as stream 
margins throughout much of the United States. 

Genus Lutrochus Erichson, 1847 

Lutrochus arizonicus Brown and Murvosh, 1970. Larvae in calcareous en- 
crustation of submerged rocks, etc.; adults usually at or just above 
water line on the downstream side of rocks or wood projecting from 
the water in riffles of streams in central Arizona. 

Lutrochus laticeps Casey, 1893. Larvae and adults as above in streams 

of high calcium content from Maryland to Michigan and eastern Oklahoma. 


Lutroahus luteus LeConte, 1852. Larvae in calcareous encrustation or be- 
neath submerged rocks; adults either at water line or on submerged 
rocks or wood in travertine or other streams with high calcium con- 
tent from central Texas and Oklahoma to eastern New Mexico, 

Genus Physemus LeConte, 1854 

Physemus minutus LeConte, 1854. Not known to be aquatic, but adults may 
be found in damp places such as stream margins in southwestern 
states from Texas to California. 

Subfamily Cephalobyrrhinae 

Genus Throsoinus LeConte, 1874 

Not known to be aquatic; adults are intertidal (two species along 

the Gulf shore of Texas and one species on the shores of southern 
California) . 

Family PSEPHENIDAE (Lacordaire, 1854) 

Subfamily Eubriinae 

Genus Acneus Horn, 1880 
(This genus merits study. Few larvae have been taken.) 

Acneus oregonensis Fender, 1951. Larvae on or under submerged rocks, 

adults along swift, rocky streams from Oregon to Olympic Peninsula 
of Washington. 

Acneus quadrimaculatus Horn, 1880. Larvae on or under submerged rocks 

in rapid sections of streams, but in pools of quiet water protected 
by boulders; adults on vegetation or rocks along swift, rocky 
streams in California and Oregon, at elevations up to about 4,000 

Genus Dicranopselaphus Guerin-Meneville, 1861 

Dicvanoipselaphus vaviegatus Horn, 1880. The larva probably occurs on or 
under submerged rocks or wood in streams; the adult near streams 
from New York, Maryland, and Pennsylvania to Illinois. Rare. (No 
one has reported the larva in the United States. It has probably 
been mistaken for that of Ectopriaj or simply overlooked.) 

Genus Ectopria LeConte, 1853 

Ectopria nervosa (Melsheimer, 1844) . Larvae on submerged rocks and wood 
in streams from Florida to Maine and Canada west to Iowa, Missouri, 
and Oklahoma; adults on vegetation along streams or taken at lights. 


Subfamily Eubrianacinae 

Genus Eubrianax Kiesenwetter, 1874 

Eubrianax edwardsi (LeConte, 1874) . Larvae on or under submerged rocks 
in California and Oregon streams up to about 6,000 feet; adults 
along stream banks. 

Subfamily Psepheninae 

Genus Psephenus Haldeman, 1853 
(Additional species from Arizona are under study. Murvosh and I are 
describing two new species.) 

Psephenus haldemani Horn, 1870. Larvae on or under submerged rocks in 
streams, adults on rocks or wood protruding from riffles, at or 
just above water line on downstream side; from California to British 
Columbia and northern Idaho at elevations up to about 4,000 feet. 

Psephenus herriaki (DeKay, 1844) . Habitats as above; in streams from 
central Alabama and Georgia northeast to Maine and Canada and west 
to eastern Oklahoma, Kansas and Wisconsin, at elevations below 2,500 
feet. Also on wave-washed shores with suitable rocks, as on the 
Bass Islands of Lake Erie. 

Psephenus murvoshi Brown, 1970. Habitats as above, in streams of cen- 
tral Arizona at elevations below 5,000 feet. 

Psephenus texanus Brown and Arrington, 1967. Habitats as above, in 

streams of central and southwestern Texas, at elevations below 2,000 
feet. These streams are typically clear, with a high calcium content. 

Family PTILODACTYLIDAE (Lacordaire, 1857) 

Genus Anahyoteis Horn, 1880 

Anchyoteis velutina Horn, 1880. Larvae in springs and rapid streams of 
northern California and adjacent Nevada; adults along or near 

Genus Anahy tarsus Guerin-Meneville, 1843 

Anahytarsus bioolor (Melsheimer, 1846) . In or near streams from Georgia 
to New York, rare. 

Genus Stenooolus LeConte, 1853 

Stenooolus scutellaris LeConte, 1853. Along streams of central 
California at elevations up to 4,000 feet. 





Compact, ovoid; head retracted within prothorax and invisible 
from dorsal view, antennae fitting into grooves of 
prosternum; tarsus with third segment lobed; claws not 
prominent; not genuinely aquatic (Fig. 16): 

CHELONARIIDAE, Chelonarium leoontei 

Head usually visible from dorsal view, though it may be 

temporarily retracted within prothorax; third segment of 
tarsus not conspicuously lobed; tarsal claws prominent .... 2 

Fig. 16- Chelonariim teaontei adult, dorsal. 

2(1) Typically hard-bodied; front coxae rounded or transverse 3 

Typically soft-bodied; front coxae exserted and projecting 

and/or hind margin or pronotum crenulate 5 

3(2) Typically very plump, convex, and ovoid; legs retractile; 

apical segment of tarsus shorter than remaining segments 
combined; middle coxae widely separated, hind coxae close 

together LIMNICHIDAE 105 

Usually more elongate; legs not retractile; apical segment 
of tarsus usually as long as other four segments combined, 
with large claws; if middle coxae are widely separate, so 
are hind coxae 4 

4(3) Anterior coxae typically globular and without exposed 

trochantin; antennae typically slender, not forming a 
pectinate or lamellate club; female genitalia symmetrical, 
with jointed, movable styli (Fig. 11); about 1-8 mm long, 

usually less than 4 mm . . . .ELMIDAE 6 

Anterior coxae transverse and with exposed trochantin; 

antennae usually short, with apical segments pectinate or 
lamellate and forming a club; female genitalia without 
styli, usually asymmetrical and resembling two knife 
blades (Figs 101, 102), functioning as ovipositors; about 
4-8 mm long ^.DRYOPIDAE 94 


5 (2) Rather broad and depressed; mandibles typically concealed; 

labrum usually not visible from in front . .PSEPHENIDAE. . . 110 
Body relatively elongate; mandibles visible; labrum usually 

visible from in front PTILODACTYLIDAE 118 

6 (4) Riparian, usually not under water; agile fliers; rather 

soft -bodied; pubescent, but without tomentum; procoxae 

transverse and with trochantin exposed LARINI 7 

Aquatic; typically slow-moving, clinging to submerged 
objects; rarely flying except at night; hard-bodied; 
with tomentum on various ventral parts; procoxae 
rounded and trochantin concealed ELMINI 10 

7 (6) Less than 4 mm long; antennae clubbed; pronotum with sub- 

lateral sulci (Fig. 17): Phanoaerus claviaomis 

More than 5 mm long; black, antennae not clubbed; pronotum 

without sublateral sulci (Fig. 18) Lara 8 

Figs 17-18 Dorsal view of adult: 17- Phanoaerus claviaomis; 
18- Lara avara. 

8 (7) From 5.5-6.5 mm long; pronotum with hind angles acute but 

scarcely more prominent than middle lobes; elytral 
pubescence uniform (Fig. 19): Lara gehringi 
From 6.8-8.1 mm long; pronotum with hind angles acute and 
prominent; alternate elytral intervals with the pubescence 
decumbent, so that the elytra appear dark with sericeous 
lines 9 

9 (8) Elytra 6.0-6.5 mm long; elytra wider in proportion to 

pronotum; pronotum with more prominent angles (Fig. 21) : 

Lara avara amplipennis 
Elytra about 5.2-5.5 mm long; elytra narrower in propor- 
tion to pronotum; pronotal angles less prominent (Fig. 20): 

Lara avara avara 


Figs 19-21 Pronotum and elytra: 19- Lara gehvingi; 20- Lara 
avara avara; 21- Lara avara amplipennis (all from Darlington, 

10 (6) Hind coxae globular and about same size as other coxae; 

posterior margin of prosternal process almost as wide 

as head ; on wood 11 

Hind coxae transverse and larger than other coxae; 

posterior margin of prosternal process much narrower 

than width of head; often on rocks or in gravel 12 

11 (10) Black; elytra with sublateral carinae; antennae with 7 

segments, enlarged at apex; pronotum without transverse 
impressions; 2.5-3.5 mm long (Fig. 22): Maoronyohus glabratus 
Conspicuously colored with black and yellow or orange; 
elytra and pronotum without sublateral carinae; 
antennae with 11 segments, filiform; pronotum with 
oblique transverse impressions at apical third; tarsal 
claw with a basal tooth; 2.1-2.6 mm long (Fig. 23): 

Ancyronyx variegata 

Figs 22-23 Dorsal view of aduit: 22- Maaronyahus glabratus; 
23- Ancyronyx variegata. 


12 (10) Antennae with 8 segments, the apical one being enlarged; 

pronotum with median longitudinal groove; elytra with 

3 sublateral carinae Zaitzevia 13 

Antennae with 10 or 11 segments, usually filiform 14 

13 (12) In cold mountain streams; 2-2.5 mm long, 0.8-1 mm wide 

(Fig. 24): Zaitzevia parvula 

In a warm spring near Bozeman, Montana; 2 mm long, 0.7 mm 

wide: Zaitzevia thermae 

14 (12) Anterior tibia with fringe of tomentum (Fig. 2) 43 

Anterior tibia without fringe of tomentum 15 

Figs 24-25 Dorsal view of adult: 24- Zaitzevia parvula; 25- Ovdobrevia 

15 (14) Elytron with an accessory stria (sutural stria confluent 

with second stria at about fifth puncture) ; granules of 
head and legs elongate; 2.2-2.4 mm (Fig. 25): 

Ovdohrevia nubifera 
Elytron without such an accessory stria; granules of head 

and legs round (Fig . 26) Stenelmis 16 

(This section is adapted from Sanderson (1938) . In identi- 
fication of species it will be helpful to know that in most 
males the inner surface of the middle tibia bears a swelling 
or row of spinules as shown in Fig. 26.) 

16 (15) From thermal waters in southern Nevada; elytra immaculate 

(5. a. aalida) or faintly trivittate (5. a. moapa) ; 
wings reduced and non-functional; body covered with 
dense, matted, greenish gray pile; antennae and palps 
testaceous; aedeagus quite similar to that of S. fuscata; 
3-3.6 mm long, 1-1.25 mm wide: Stenelmis calida 
From east of the Rocky Mountains 17 


Fig. 26- Stenelmis arenata adult showing appearance of middle 
tibia of female on the left and of the male on the right (to 
illustrate means of distinguishing sexes if genitalia are not 
visible) . 

17 (16) Last tarsal segment distinctly longer than the other four 
combined, the last segment usually suddenly dilated 
beyond the middle (Fig. 27); tarsal claws relatively robust 

(Fig. 28) Humerosa-sinuata group 28 

Last tarsal segment not distinctly longer than the other 
four combined, the last segment not as noticeably 
dilated (Fig. 29); tarsal claws relatively slender 
(Fig. 30) Crenata group 18 

27 29 

Figs 27-35 Tarsus of Stenelmis species: 27- Apical 
segment of S. vitti-pennis; 28- S. markeli; 29- Apical 
segment of S. sandersoni; 30- S. lateralis. Aedeagus (male 
genitalia) of Stenelmis species: 31- S. sexlineata^ dorsal 
aspect; 32- 5. arenata; 33- S. exigua; 34- S. heameri; 
35- S. lateralis (all from Sanderson). 


18 (17) Each elytron with 3 longitudinal vittae; 3.2-3.6 mm long, 

1.25-1.4 mm wide (Fig. 31): Stenelmis sexlineata 

Each elytron with no more than one vitta or elytron 

bimaculate 19 

19 (18) Humeral spot or vitta embracing vunbone of elytron 22 

Humeral spot or vitta on inside of sixth interval 20 

20 (19) Body very robust, and with the elytral spots or stripe 

wider, covering considerably more than the fifth 
interval; third interval sharply elevated at base; 
elytron with entire vitta or bimaculate; 3.0-3.35 mm 
long, 1.2-1.35 mm wide (Figs 26, 32): Stenelmis orenata 
Body very elongate, with the elytral spots or stripe 
narrower, covering but little more than the fifth 
interval; third interval but slightly elevated at base 
and this elevation very short 21 

21 (20) Median lobe of aedeagus distinctly constricted at middle 

(Fig. 33); 2.85-2.9 mm long, 1-1.1 mm wide: Stenelmis exigua 
Median lobe of aedeagus more nearly parallel (Fig. 34); 

3.2-3.4 mm long, 1.2-1.25 mm wide: Stenelmis heamevi 

22 (19) Vitta very broad and covering nearly all of the space 

between the first and sixth intervals; 2.65-3 mm 
long, 0.95-1.1 mm wide (Fig. 35): Stenelmis lateralis 
Vitta narrower and never extending medially beyond the 

second or third interval 23 

23 (22) Size larger: 3.2-3.6 mm; lower margin of last tarsal 

segment with a conspicuous angular process (Fig. 29) .... 24 
Size smaller: 2.6-3.25 mm; lower margin of last tarsal 

segment without such a process (Fig. 27) 25 

24 (23) Apical abdominal emargination equal to width of last 

tarsal segment; tibiae testaceous only at base; elytron 
bimaculate; 3.3-3.6 mm long, 1.3-1.5 mm wide: 

Stenelmis aoncinna 
Apical emargination very inconspicuous and much less 

than width of last tarsal segment; tibiae and apices of 

femora testaceous; bimaculate; 3.2-3.5 mm long, 1.25- 

1.5 mm wide (Fig. 37): Stenelmis sandersoni 

25 (23) Basal tubercle of pronotum elongate and carinate 26 

Basal tubercle of pronotum only slightly elongate 

and never carinate 27 


Figs 36-41 Aedeagus of Stenelmis species: 36- S. aonoinna; 

37- S. sandersoni; 38- S. mera; 39- S. knobeli; 40- 5. bioarinata; 

41- 5. douglasensis (all from Sanderson). 

26 (25) Legs testaceous; elytra twice as long as body width; 

elytron bimaculate; 2.8-3 mm long, 1-1.1 mm wide: 

Stenelmis exilis 
Legs entirely or partially dark; elytra less than twice 
as long as wide; elytron vittate but with vitta clouded 
at middle; 2.6-2.85 mm long, 1-1.2 mm wide (Fig. 38): 

Stenelmis mera 

27 (25) Each elytron distinctly bimaculate; 2.75-3 mm long, 

1-1.05 mm wide (Fig. 39): Stenelmis knobeli 

Each elytron with an entire vitta; 2.8-3.25 mm long, 

1.1-1.25 mm wide (Fig. 40): Stenelmis biaarinata 

28 (17) Femora distinctly granulate 30 

Femora punctulate, not at all granulate 29 

29 (28) Elytral vitta complete from base to apex; lateral 

processes on median lobe of aedeagus evenly rounded 
(Fig. 41); 3.35-3.6 mm long, 1.2-1.5 mm wide: 

Stenelmis douglasensis 
Elytron distinctly bimaculate; processes on median 
lobe of aedeagus subangulate anteriorly (Fig. 42); 
3.25-3.6 mm long, 1.25-1.4 mm wide: Stenelmis grossa 

30 (28) Elytra immaculate •• 31 

Elytra maculate or vittate 33 

31 (30) Smaller (less than 2.7 mm); median band of head as 

wide as two lateral ones combined; 2.3-2.7 mm long, 
0.7-0.9 mm wide (Fig. 43): Stenelmis parva 

Larger (over 2.7 mm long and 1 mm wide); median band 

of head but little wider than either lateral band 32 


Figs 42-48 Aedeagus of Stenelmis species: 42- S. grossa; 

43- S. parva; 44- S. fusaata; 45- S. hungevfordi; 46- S. himerosaj 

47- 5. mivahilis ; 48- S. antennalis (all from Sanderson) . 

32 (31) Lateral processes on penis (median lobe of aedeagus) 

present and distinct (Fig. 44); 3.25-3.4 mm long, 
1.15-1.25 mm wide: Stenelmis fusoata 

Lateral processes of median lobe very inconspicuous 
(Fig. 45); 2.7-2.8 mm long, 1-1.1 mm wide: 

St&nelmis hung erf ordi 

33 (30) Humeral spot or vitta distinctly embracing umbone 34 

Humeral spot or vitta on inside of sixth interval 35 

34 (33) Femora and tibiae entirely gray; elytral vitta usually 

entire, though somewhat clouded at middle; palpi 
testaceous; 2.3-2.7 mm long, 0.95-1.1 mm wide 
(Fig. 46) : Stenelmis humerosa 

Femora gray, tibiae testaceous; elytron distinctly 
bimaculate; palpi dark brown to black; 2.7-2.9 mm 
long, 1.1-1. 12 mm wide (Fig. 47): Stenelmis mivahilis 

35 (33) Antennae and palpi testaceous 38 

Antennae or palpi, or both, dark brown to black 36 

36 (35) Palpi testaceous; last 6 or 7 segments of antenna 

shining black; elytron bimaculate; 2.5-2.7 mm long, 
1 mm wide (Fig. 48): Stenelmis antennalis 

Palpi usually dark brown to black, the antennae usually 

lighter 37 


37 (36) Lateral processes about one third the width of median 

lobe (Fig. 49); elytron usually distinctly bimaculate, 
but occasionally vitta is entire; 2.4-2.65 mm long; 
0.95-1.05 mm wide: Stenelmis musgravei 

Lateral processes about two thirds the width of median lobe 
(Fig. 50); elytron distinctly bimaculate; 2.7-3.2 mm long, 
1.1-1.25 mm wide: Stenelmis quadrimaculata 


Figs 49-54 Aedeagus of Stenelmis species: 49- S. musgrccoei; 
50- S. quadrimaculata; 51- 5. deoovata; 52- 5, vittipennis; 
53- S. aonvexula; 54- S. markeli (all from Sanderson) . 

38 (35) Sides of pronotum in anterior third divergent, the 

apical angles subtruncate instead of acute; elytron 
maculate, with vitta narrow and occupying little 
more than fifth interval; lateral processes of 
penis resembling those of S. hwnerosa; 3.2-3.45 mm 
long, 1.2-1.35 mm wide: Stenelmis sinuata 

Sides of pronotum in anterior third parallel or 

convergent 39 

39 (38) Lateral processes of median lobe of aedeagus present 

and conspicuous 41 

Lateral processes of median lobe absent or very 

inconspicuous 40 

40 (39) Elytral stripe entire; median lobe of aedeagus without 

lateral processes (Fig. 51); 2.87-3 mm long, 1.1-1.15 
mm wide: Stenelmis deoovata 

Elytron immaculate or with small, faint humeral and 

apical spots; median lobe of aedeagus with narrow and 
inconspicuous lateral processes (Fig. 45); 2.7-2.8 mm 
long, 1-1.1 mm wide: Stenelmis hunger fordi 

41 (39) Lateral processes of median lobe of aedeagus subangulate 

anteriorly (Fig. 52); elytron with vitta entire; 3-3.4 
mm long, 1.1-1.35 mm wide: Stenelmis vittipennis 
Processes of median lobe evenly rounded 42 


42 (41) Lateral processes of penis as wide as parameres near 

apex (Fig. 53); body more convex; elytron usually 
with very faint humeral and apical spots; middle tibia 
of male without the enlargement or spiny ridge on 
inner side which is typical of most species of 
Stenelmis; 2.75-3.1 mm long, 1.1-1.12 mm wide: 

Stenelmis oonvexuta 
Lateral process of penis about half the width of 
paramere near apex (Fig. 54); body less convex; 
elytron with vitta entire, though slightly narrowed 
at middle; 3-3.25 mm long, 1.17-1.3 mm wide: 

Stenelmis markeli 

43 (14) Lateral margin of fourth or iifth abdominal stemite 

produced as a prominent lobe or tooth which is bent 
upward to clasp the epipleuron; epipleuron widened to 
receive tooth, then usually narrowing abruptly toward 

apex '. 56 

Lateral margin of abdominal stemites not produced into 
a prominent upturned tooth; epipleuron usually tapering 
uniformly toward apex 44 

44 (43) Pronotum with sublaterai carinae 45 

Pronotum smooth, without sublaterai carinae 49 

45 (44) Prostemum projecting beneath head; epipleuron extending 

to middle of fifth abdominal segment; black; 2.5-2.6 
mm long, 1.2-1.3 mm wide (Figs 55, 56): Rhizelmis nigra 
Prostemum not projecting beneath head; epipleuron ending 
at base of fifth abdominal segment; less than 2.3 mm 
long 46 

Figs 55-"56 Rhizelmis nigra adult: 55- dorsal; 56- ventral 


46 (45) Pronotal carinae forked at base (Fig. 57) . . Cleptetmis ... 47 

Pronotal carinae not forked 48 

47 (46) Elytra immaculate and black (humeral angle may be 

paler); 1.7-2.3 mm long, 1-1.2 mm wide: Cleptelmis addenda 
Elytra black with humeral and subapical red spot; 

1.8-2.2 mm long, 1-1.2 mm wide (Fig. 57): Cleptelmis ornata 

Fig. 57- Cleptelmis ornata adult, dorsal. 

48 (46) Sides of pronotum converging from base; body rather 

spindle-shaped; black, each elytron with a broad 
humeral and an oblique, narrow subapical spot; tarsi 
and claws prominent; 2 mm long, 0.9 mm wide (Figs 
58, 59) : Atraatelmis wauona 

Sides of pronotum parallel or divergent at base, 

strongly convergent apical ly; hump-backed; black, 
elytra black to red, uniformly colored or with basal 
half red, with or without broad apical red spots; tarsi 
and claws not unusually prominent; 1.8-2.2 mm long, 
1.1-1.2 mm wide (Fig. 60): Ampumixis dispar 

49 (44) Maxillary palpi 3-segmented; markings, if present, 

transverse (Fig. 61) Narpus 50 

Maxillary palpi 4-segmented; markings, if present, 

longitudinal (Fig. 62) Dubiraphia 52 

50 (49) Slender, more than two and one half times as long as 

wide; 3-4 mm long, 1.1-1.4 mm wide; sides almost 
parallel; black: Narpus angustus 

Relatively plump, less than two and one half times as 

long as wide; sides convex 51 


Figs 58-59 Atractelmis waxoona adult: 58- dorsal; 
59- ventral. 

Figs 60-61 Dorsal view of adult: 60- Ampumixis 
dispar; 61- Narpus conaolor. 

51 (50) Uniformly black with bronze luster; pronotal punctures 

at middle separate by little more than their own 
diameters; 3.4 mm long, 1.4 mm wide: Narpus arizonious 
Elytra black to red, usually with black band across 
middle; pronotal punctures at middle separated by 
twice their own diameters; 3.2-4.2 mm long, 1.4-1.9 
mm wide (Fig. 61) : Narpus conaolor 

52 (49) Large (2.6-3.3 mm long, 1-1.2 mm wide); eastern; 

elytron black, with broad testaceous vitta; pronotum 
darker testaceous: Dubiraphia bivittata 

Smaller (1.7-2.5 mm long, 0.65-0.85 mm wide); 

eastern or western 53 


53 (52) West of the Rocky Mountains (continental divide) 54 

East of the Rocky Mountains (continental divide) 55 

54 (53) Elytron dark brown, with at most faint yellowish 

humeral or subapical spots; 1.8-2.5 mm long: 

Dubivaphia brunnesaens 
Elytron black with humeral and apical light yellow 
spots, sometimes united to form a vitta; 2.1-2.3 mm 
long: Dubiraphia giulianii 

55 (53) Black, elytron with humeral and apical rufous or 

testaceous spots, which may be united to form a 
vitta; 1.7-2.5 mm long, 0.65-0.85 mm wide (Fig. 62): 

Dubiraphia quadrinotata 
Brownish, elytron with a broad testaceous vitta; 

1.8-2.5 mm long, 0.7-0.85 mm wide: Dubiraphia vittata 

56 (43) Tooth which clasps epipleuron arising from lateral margin 

of fifth abdominal sternite 57 

Tooth which clasps epipleuron arising from apical 
(posterior) lateral margin of fourth abdominal 
sternite 76 

Figs 62-63 Dorsal view of adult: 62- Dubiraphia quadrinotata; 
63- Etsianus texanus. 

57 (56) Elytron at base with a short accessory stria between 
sutural and second major striae (Fig. 63); testis 

trilobate Etsianus 

Elytron without such an accessory stria, testis 

usually bilobate 



58 (57) Small (3.1-3.8 mm long, 1.2-1.5 mm wide); black, with 

antennae and tarsi rufous, palp rufo-testaceous; penis 
extending beyond apices of parameres more than one 
third the length of parameres: Elsianus shoemakei 
Larger (over 4 mm long) ; penis extending beyond apices of 
parameres less than one quarter the length of the 
parameres 59 

59 (58) In Arizona; rufous to black; 4-5.2 mm long, 1.7-2.1 mm 

wide (it may be that more than a single species is 
represented by these measurements; very few specimens 
have been taken) : Elsianus moestus 

In Texas and eastern New Mexico; rufous to black; 4-5.4 
mm long, 1.7-2 mm wide (Fig. 63) (further study may 
reveal this species to be synonymous with E. moestus) : 

Elsianus texanus 

60 (57) Elytron with one sublateral carina; pronotum without 

oblique sculpturing 61 

Elytron with two sublateral carinae (rarely only one in 
Micro ayllo epus , which has oblique sculpturing on 
posterior half of pronotum) 62 

61 (60) Posterior half of pronotum divided by a conspicuous 

median longitudinal impression; pronotum with a 

transverse impression slightly anterior to middle; 

brown to black; 2.6-3.3 mm long, 1-1.2 mm wide (Fig. 64): 

Neoeylloepus boeseli 
Pronotum undivided except by transverse impression at 
anterior two-fifths; testaceous; 1.5-1.7 mm long, 0.5- 
0.6 mm wide (Fig. 65): Neoelmis caesa 

Figs 64-65 Dorsal view of adult: 64- Neooylloepus boeseli; 
65- Neoelmis oaesa. 


62 (60) Hypomeron of pronotum with a belt of tomentum extend- 

ing from coxa to lateral margin; pronotum with a 
shallow median longitudinal impression but with no 
transverse impressions; testaceous to black; 1.7-2.1 
mm long, 0.7-0.85 mm wide (Fig. 66): 

Hexaaylloepus ferrugineus 
Hypomeron with or without tomentum, but if present it 

does not reach lateral margin 63 

63 (62) Prosternal process broad and truncate; pronotum without 

median longitudinal impression, usually with transverse 
impression at middle; pronotal hypomeron with tomentum 
near coxa; body usually plump; mandible with a lateral 

lobe (Fig. 5) Eeterelmis 64 

Prosternal process relatively narrow, elongate with 
apex tapering or rounded; pronotum with median 
longitudinal impression; hypomeron without tomentum; 
body not plump 66 

64 (63) Basal segment of each tarsus with two closely appressed, 

short, stout spines on inner apex; reddish brown to 
black; pronotum with little or no transverse impression 
at middle; 2.5-3.3 mm long, 1.1-1.5 mm wide: 

Eeterelmis obesa 
Basal segment of tarsus without such spines on inner 
apex; pronotum with transverse impression at middle; 
less than 2 . 5 mm long 65 

Figs 66-67 Dorsal view of adult: 66- 

67- Eeterelmis vulnerata. 

Eexaaylloepus ferrugineus; 

65 (64) Medial surface of parameres of aedeagus bearing a row of 
delicate hairs; brown to black; 1.9-2.2 mm long, 1- 
1 . 1 mm wide: Eeterelmis glabra 

Medial surface of parameres devoid of hairs; brown to 
black; 1.8-2.35 mm long, 0.9-1.15 mm wide (Fig. 67): 

Eeterelmis vulnerata 


66 (63) 

67 (66) 

Pronotum with a transverse impression at anterior two- 
fifths; mandible with a lateral lobe as in Fig. 5; 
epipleuron without tomentum; small, less than 2.3 mm 
long (Fig. 70) Microoylloepus 

Pronotum without such a transverse impression; mandible 
without a lateral lobe; epipleuron with tomentum; 
larger, at least 2.3 mm long (Fig. 68).... Cylloepus . . 



Pronotum wider than long; fifth elytral interval not 
carinate; metastemum with a short carina at middle 
near posterior margin; black, elytron usually with two 
large reddish spots; 2.3-3 mm long; 1.2 mm wide (Figs 
68, 69) : Cylloepus parkeri 

Pronotum slightly longer than wide; fifth elytral interval 
partly carinate; metasternum depressed but without a 
posterior median carina; reddish brown to black; 3.5- 
4.3 mm long, 1.5-1.65 mm wide: Cylloepus abnormis 

Figs 68-69 Cylloepus parkevi adult: 68- dorsal; 69- ventral. 

68 (66) Pronotum longer than wide; wing usually reduced, 

shorter than elytron; from warm springs 69 

Pronotum usually wider than long; wing functional, 

when extended longer than elytron; 1.65-2.2 mm long, 
0.68-0.9 mm wide (Fig. 70).., Microoylloepus pusillus . . . 72 

69 (68) Elytron with 1 sublateral carina; elytra only slightly 

wider than pronotum; sculpturing of pronotum reduced; 
black; 1.4-1.7 mm long, 0.5 mm wide; from warm spring in 
northwestern Nevada: Microoylloepus thermarum 

Elytron with 2 sublateral carinae; elytra distinctly 

wider than pronotum; reddish to black 70 


Figs 70-71 Dorsal view of adult: 70- Miorooylloepus pusiltusj 
ll-OuZimni-us Zatiusaulus. 

70 (69) From warm springs in Montana (near Bozeman) ; black; 2 mm 

long, 0.68-0.7 mm wide: Miorooylloepus browni 

From warm springs in southeastern Nevada; reddish black, 

1.7-1.9 mm long, 0.7-0.8 mm wide. Miorooylloepus mo opus . 71 

71 (70) Wing greatly reduced, not exceeding one-third of 

abdominal length: Miorooylloepus moapus moapus 

Wing less reduced, slightly over half of abdominal 

length: Miorooylloepus moapus fraxinus 

72 (68) Elytron reddish to black, without distinct markings 73 

Elytron with vitta or spots 74 

73 (72) In western states: Miorooylloepus pusillus similis 

In southeastern Gulf coastal plain: 

Miorooylloepus pusillus lodingi 

74 (72) Elytron with a vitta: Miorooylloepus pusillus aptus 

Elytron with spots 75 

75 (74) Elytron with humeral and apical spots: 

Miorooylloepus pusillus pusillus 
Elytron with only humeral spot: 

Miorooylloepus pusillus perditus 

76 (56) Pronotum with sublateral carina extending from base to 

anterior margin; elytron with 3 sublateral carinae; 
brown to black; 1.25-1.6 mm long, 0.65-0.8 mm wide 
(Fig. 71): Oulimnius latiusoulus 
Pronotum with sublateral carina absent or not extending 
beyond about middle; elytron without sublateral 
carinae; larger species, longer than 1.6 mm 77 


77 (76) Pronotum smooth, without or with only a trace of 

carinae; body elongate and spindle-shaped; black, 
elytron with two oblique yellowish spots; legs long, 
claws prominent and recurved; 2-2.6 mm long, 0.95- 
1 . 1 mm wide (Fig. 72): Gonielmis dietvidhi 
Pronotum with short sublateral carinae 78 

78 (77) 

79 (78) 

Figs 72-73 Dorsal view of adult: 72- Gonielmis dietvidhi; 
73- Promoresia elegans. 

Body rather elongate; tarsi and claws long and prominent; 
lateral and posterior margins of pronotum smooth; 
eastern (Fig . 73) Promoresia 

Body plump; tarsi and claws not conspicuously enlarged; 
lateral margin of pronotum usually slightly serrate, 
posterior margin usually with many small, closely- 
placed teeth 



Black, elytron bimaculate, both spots very elongate and 
oblique, the anterior spot extending from the humerus 
posteromedial ly to second stria and terminating acutely 
near middle of elytron, the posterior spot extending 
from near middle of elytron (lateral to apex of 
anterior spot) posteromedial ly almost to sutural 
interval and apex of elytron; 2.1-2.4 mm long, 0.9-1 mm 
wide (Fig. 73): Promoresia elegans 

Black, elytron bimaculate, the anterior spot broadly rounded, 
extending posteriorly no more than one third of elytral 
length; subapical spot elongate and oblique, but shorter 
than in previous species; 2-2.4 mm long, 0.9-1.1 mm wide: 

Promoresia tardella 


80 (78) Convex, giving a ratHer hump-backed appearance, with 
sutural intervals slightly raised; with third or 
fourth elytral stria converging and merging with 
second or third stria at about apical third; major 
striae entire, extending to apex of elytron; antennae 
with 10 or 11 segments, last 3 somewhat enlarged; apex of 
fifth abdominal sternite usually somewhat truncate 
or emarginate; tarsal claws relatively slender; in 

western mountains (Fig. 74) Heterlirmius 81 

Less convex; sutural interval usually not raised; 

elytral striae not ordinarily merging as described 
above, either being entire or becoming obsolete in 
posterior portion of elytron; antennae with 11 segments, 
the last 3 less enlarged; apex of fifth abdominal 
sternite usually evenly rounded; claws somewhat 

larger and more curved (Fig. 75) .... Optioservus 

[This section is largely based upon Collier (1969).] 82 

Figs 74-75 Dorsal view of adult: 74- Heterlirmius 
corpulentus; 75- Optioservus ovalis. 

81 (80) Antenna with 11 segments; pronotum black; elytron 
reddish to black, often reddish or yellowish in 
basal half shading to brown or black and with a 
diffuse lighter spot apically; 2-2.5 mm long, 1.1- 
1.3 mm wi e (Fig. 76): Ueterlivmius koehelei 

Antenna with 10 segments; pronotum black; elytron 
brown to black, often reddish at base and in a 
rather faint apical spot; 2.4-2.9 mm long, 1.25- 
1.45 mm wide (Fig. 74): Heterlimnius corpulentus 

82 (80) Elytra immaculate, with no vittae or spots 
Elytra with vittae and/or spots 



83 (82) Small, 2-2.1 nun long, 1 mm wide; slightly humped in 
side view; brown to black; eastern (Fig. 77) : 

Optioservus aryophilus 
Larger, at least 2.2 mm long; not noticeably humped 

in side view 84 

84 (83) 

Figs 76-82 Outline of adult pronotum and elytron: 

76- Heterti-mnius koebelei; 77- Optioservus aryophilus; 

78- 0, irrmunis; 79- 0. divergens; 80- 0. pecosensis; 

81- 0. trivittatus; 82- 0. sandersoni (all from Collier), 

Eastern; strial punctures on elytra deep; 2.2-2.4 mm 
long, 1.2-1.3 mm wide; brown to black (Fig. 78): 

■Optioservus irmrunis 
Western 85 

85 (84) Penis tapering gradually to a subacute apex; elytral 

striae lightly punctured; brown to black, with elytra 
at times lighter than head and thorax; 2.2-2.5 mm 
long, 1-1.1 nun wide (Fig. 79): Optioservus divergens 
Penis more finger-shaped, tapering abruptly to a 
rounded apex; strial punctures deeper; uniformly 
shiny black; 2.4-2.6 mm long, 1-1.2 mm wide (Fig. 80): 

Optioservus peoosensis 

86 (82) Elytron with sutural vitta extending to apical third 87 

Elytron without sutural vitta 89 

87 (86) Elytron also with yellow vitta from humerus almost to 

apex (Fig. 81), 1.65-2.1 mm long, 0.9-1.1 nun wide: 

Optioservus trivittatus 
Without humeral vitta 88 

88 (87) Sutural vitta narrow; humeral spot discrete; apical 

spot long and narrow, subvittate (Fig. 82); 2.6 mm 
long, 1.3 mm wide: Optioservus sandersoni 

Sutural vitta broadened anteriorly and combined with 
humeral spot, apical spot elongate (Fig. 83); 2.3 mm 
long, 1.2 mm wide: Optioservus ozarkensis 


89 (86) Elytron bimaculate 92 

Elytron with an elongate humeral spot or with a 

vitta extending from humerus almost to apex 90 

90 (89) Large, 2.8-3.1 mm long, 1.4-1.5 mm wide; elytral 

vitta extending almost to apex, at times bright 
yellow; pronotal carinae rather short and feeble 
(Fig. 84) : Optioservus fastiditus 

Smaller, less than 2.7 mm long; pronotal carinae 

well developed and extending at least to basal third.... 91 

91 (90) 

In far west; elytron with elongate humeral spot or 

short vitta (Fig. 85); elytra with grizzled appearance 
due to long golden hairs; 2.1-2.5 mm long, 0.9-1.4 mm 
wide: Optioservus aanus 

Eastern; elytron with vitta from humerus almost to 
apex (Fig. 86); not grizzled; 2.3-2.6 mm long, 
1.2-1.3 mm wide: Optioservus amptiatus 

Figs 83-89 Outline of adult pronotum and elytron of Optioservus 
species: 83- 0. ozarkensis; 84- 0. fastiditus; 85- 0. aanus; 
86- 0. amptiatus; 87- 0. ovalis; 88- 0. quadrimaaulatus ; 
89- 0. seriatus (all from Collier). 

92 (89) Eastern; elytral spots almost forming a vitta in some 

specimens (Figs 75, 87); 2.4-2.6 mm long, 1.2-1.4 mm 
wide : Optioservus ovalis 
Western; elytral spots widely separated 93 

93 (92) Relatively broad, elytra noticeably wider than pronotum; 

humeral spot larger, usually reaching second stria 
(Fig. 88); 1.8-2,2 mm long, 1-1.1 mm wide: 

Optioservus quadrimaaulatus 
More elongate, elytra scarcely wider than pronotum; 

humeral spot narrower, usually not reaching medially 

beyond third stria (Fig. 89); 1.8-2,2 mm long, 0.8- 

. 9 mm wide : Optioservus seriatus 


94 (4) Pronotum on each side with a conspicuous, complete 
sublateral longitudinal sulcus; pubescent; brown; 
about 4.5 mm long, 1.75 mm wide (Fig. 90) : Dry ops arizonensis 
Pronotum without such a sublateral sulcus 95 

Figs 90-91 Dorsal view of adult: 
91- Pelonomus obsourus. 

90- Dryops arizonensis; 

95 (4) Second segment of antenna not enlarged; antennae 

pubescent, as are head and body; bases of antennae 
very close together; both third and fourth segments 
of maxillary palp very elongate; without tomentum; 
reddish to dark brown; 4.8-6.5 mm long, 2-2.5 mm 
wide (Fig. 91) : Pelonomus obsourus 

First, and, even more, second segment of antenna 

enlarged and heavily sclerotized, forming a shield 
beneath which remaining segments may be retracted and 
protected; bases of antennae widely separated; parts 

of body and legs with tomentum (Fig. 92) Heliohus 

[This section of the key is largely based upon 

Musgrave (1935) .] 96 

96 (95) Pubescence of last abdominal sternite different from 

that of preceding stemites, the last sternite often 

appearing bare 99 

All abdominal sternites similarly and densely 

pubescent (tomentose) 97 

97 (96) Male genitalia (Figs 93, 94) flattened dorsoventrally; in 

lateral aspect paramere not enlarged apically; in dorsal 
aspect penis acutely pointed at apex; female genitalia 
(Fig. 95) relatively streamlined; black; 5.2-7.25 mm 
long, 2.15-3 mm wide: Heliohus oonfluentus 
Male genitalia not flattened; paramere enlarged at apex; 
penis not acutely pointed; female genitalia with tip of 
ovipositor (hemistemite) turned up more abruptly 98 


Fig. 92- Helichus lithophilus adult, dorsal, 

93 94 95 

Figs 93-98 Helichus aonfluentus : 93- aedeagus, dorsal aspect; 94- 
aedeagus, lateral aspect, left side (from Musgrave) ; 95- female genitalia, 
lateral aspect, left side. H. irrmsi: 96- aedeagus, dorsal aspect; 97- 
aedeagus, left lateral aspect; 98- female genitalia, left lateral aspect 
(all from Hinton) . 

98 (97) Paramere of male in lateral aspect with apex abruptly- 
enlarged (Figs 96, 97); ovipositor of female shorter 
and broader (Fig. 98); black; 5.9-8 mm long, 2.4-3.3 
mm wide: Helichus immsi 

Paramere in lateral aspect with apex gradually en- 
larged, aedeagus less robust (Figs 99, 100); 
ovipositor longer, narrower, and with a more 
digitate ventral process (Figs 101, 102); black; 
about 6-8 mm long, 2.5-3.2 mm wide: Helichus productus 


99 (96) Uniformly covered with fine, silky pubescence; male 

genitalia very elongate and slender (Figs 103, 104); 
brown to black; 4.4-5.8 mm long, 2-2.5 mm wide: 

Eelichus lithoTphilus 
Not uniformly covered with fine, silky pubescence 100 





Figs 99-104 Eelichus produotus : 99- aedeagus, dorsal aspect; 
100- aedeagus, right lateral aspect; 101- female genitalia, left 
lateral aspect; 102- female genitalia, dorsal aspect (all from 
Hinton) . Aedeagus of H. lithophilus: 103- dorsal aspect; 
104- left lateral aspect (all from Musgrave) . 

100 (99) Thorax abruptly depressed behind middle; a space in 

frontof the scutellum glabrous or almost glabrous 101 

Thorax gradually depressed; without glabrous space in 

front of scutellum 102 

101 (100) Glabrous space of thorax shining; first stria of 

elytra almost impunctate, or at most with small 
punctures not reaching base; male genitalia long 
and narrow, acutely tipped (Figs 105, 106); brown 
to black; 4.3-5.5 mm long, 2-2.5 mm wide: Heliohus basalis 
Glabrous space of thorax alutaceous; punctures of 
first stria larger and often reaching to base of 
elytron; male with a tooth-like process on antero- 
medial surface of hind coxa; male genitalia with 
stouter basal piece, parameres blunt-tipped (Figs 
107, 108); brown to black, with bronzed pubescence; 
about 4.5-5.5 mm long; 2.2-2.5 mm wide: 

Eelichus fastigiatus 


102 (100) Thorax with fovea on each side behind middle; para- 
meres of male neither decurved nor recurved near 
apex (Figs 109, 110); brown to black; 4.5-6.3 mm 

long, 2-3 mm wide Heliahus striatus 103 

Thorax without foveae 104 




Figs 105-114 Aedeagus of Heliahus species: 105- H, hasalis, dorsal 
aspect; 106- H. basalis, left lateral aspect; 107- H. fastigiatus^ 
dorsal aspect; 108- H. fastigiatuSj left lateral aspect; 109- H. 
striatus J dorsal aspect; 110- H. striatus j left lateral aspect; 
111- H. triangularis, dorsal aspect; 112- H. triangularis, left 
lateral aspect; 113- H. suturalis, dorsal aspect; 114- E. suturalis, 
left lateral aspect (all from Musgrave) . 

103 (102) Elytron with alternate intervals more convex or 

raised: Heliahus striatus striatus 

Elytron with intervals uniformly convex: 

Heliahus striatus foveatus 

104 (102) Elytron uniformly and granularly pubescent; para- 

meres of male slightly recurved (turned upward) near 
apex and not acutely pointed at tips; basal piece 
conspicuously curved (Figs 111, 112); gray or brown 
to black; 5-6.1 mm long, 2.25-2.6 mm wide: 

Heliahus triangularis 
Elytron with sutural interval less pubescent; para- 
meres more elongate, decurved toward apex, acutely 
pointed as seen in dorsal aspect; basal piece not 
conspicuously curved (Figs 113, 114); reddish brown 
to black, quite variable in size and general aspect, 
about 3.6-5.3 mm long, 1.7-2.3 mm wide (much smaller 
than listed here in parts of Mexico and central 
America) : Heliahus suturalis 


105 (3) Pronotal hypomeron with a transverse or oblique ridge; 

body plump and convex; near streams... LIMNICHINAE ... 106 
Hypomeron without a ridge; body more elongate; on 

ocean mudflats or beaches (Fig. 115) ... CEPHALOBYRRHINAE 

Throsoinus (species not 

included in key since they seem unrelated to water quality) 

106 (105) Antennae distinctly clubbed; pronotum with smooth 

anterolateral cavities for reception of antennae; 
ovoid and compact; shiny reddish to black; 0.8-1 mm 
long, 0.65-7 mm wide: Physemus minutus 

Antennae not clubbed; pronotum without cavities for 

reception of antennae; usually well over 1 mm long ... 107 

Figs 115-116 Dorsal view of adult: 115- Throsoinus schwartzi; 
116- Linmiohus sp. 

107 (106) Small (1.2-2.3 mm long); antenna slender, with 10 

segments; first abdominal stemite with grooves for 
reception of folded hind legs (Fig. 116) : Lirmichus 
(Although 28 species have been described from the United 
States, none are known to be aquatic either as larvae or 
adults, so no attempt is made here to provide a key to 
Larger (2.5-4.2 mm long); antenna with 11 segments, 
the first two enlarged and the remaining nine sub- 
pectinate; first abdominal sternite without grooves 
for the reception of folded legs (Fig. 117) .Lutroahus . .108 

108 (107) Apical segment of maxillary palp subequal in width to 

apical segment of labial palp; densely pubescent with a 
yellowish cast, but dark brown where cuticle is exposed; 
3-4.2 mm long, 1.75-2.3 mm wide: Lutroahus arizonicus 
Apical segment of maxillary palp not over three 

quarters as wide as that of labial palp 109 


109 (108) 

110 (5) 

111 (110) 

112 (111) 

Margin of clypeus emarginate; pubescence of dorsum 
thinner; eastern; 2.8-3.8 mm long, 1.5-2.1 mm wide: 

Lutroahus latioeps 

Margin of clypeus straight; dorsal pubescence dense 
and yellowish; southwestern; 2.5-3.5 mm long, 1.5- 
2.1 mm wide (Fig. 117): Lutroahus luteus 

Figs 117-118 Dorsal view of adult: 117- 
tuteus; 118- Acneus quadrimaGulatus male, 


Posterior margin of pronotum crenulate or finely 
beaded; males with at least the anterior claw on 
each foot forked at apex (this requires high 
magnification and the proper angle to observe) ; 
adults not aquatic EUBRI INAE 

Posterior margin of pronotum smooth 



Prostemum narrow, depressed between coxae; antenna 
with third joint at least as long as either the 
first two or next three combined; male with 
flabellate antennae (Fig. 118); female larger than 
male and with serrate antennae; tarsal claws of 
female not toothed at base Acneus 

Prostemum of moderate width, not depressed between 
coxae; tarsal claws of both sexes with a basal 
tooth; antenna of male not flabellate 



Elytron pale, with 7 blackish spots; mesosternal 
process widely concave; male 3.5 mm long: 

Acneus oregonensis 

Elytron dark brown or black with 2 pale spots which 
do not reach the elytral suture; these spots may be 
joined by a pale marginal loop; sutural interval may 
be lighter; 3.5-4.5 mm long, 2.1-2.8 mm wide (Fig. 
118) : Acneus quadrimaaulatus 


Figs 119-120 Dorsal view: 119- Eatopria nervosa 
female; 120- Dicranopselaphus sp. male. 

113 (111) Tarsi slender, fourth joint smaller than third and 

not prolonged beneath fifth; form, color, and 
pattern variable, but females larger than males and 
with antenna filiform to feebly serrate whereas 
antenna of male is serrate to subpectinate; brown 
to black, often with yellow or orange on much of 
pronotum; 3-5 mm long, about 2-3 mm wide (Fig. 119) : 

Eatopria nervosa 
Tarsi slightly dilated, second, third, and fourth 
joints feebly emarginate, the fourth slightly pro- 
longed beneath the fifth; antenna of male serrate to 
feebly pectinate; brownish, thorax darker, elytra cloud- 
ed and with pale, anastomosing lines; male about 3 mm 
long (Fig. 120): Dicranopselaphus variegatus 

114 (110) Head usually hidden beneath broadly expanded 

pronotum; base of claws with a membranous appen- 
dage nearly reaching to tip of claw; antenna of 
male pectinate (Fig. 121), that of female serrate; 
testaceous to black; 3-4.5 mm long, 2-2.5 mm wide: 

Eubrianax edwardsi 
Head visible from above; base of claws without mem- 
branous appendage; antenna of female moniliform, 
that of male subserrate to serrate; brown to black 
(Fig. 122) Psephenus 115 

115 (114) Anterior margin of head distinctly bisinuate 

(medially emarginate) ; ventral sclerite of penis 
almost as wide as long, emarginate at base (Fig. 
123); about 4-5.5 mm long, 1.7-3.2 mm wide (Fig. 122): 

Psephenus texanus 
Anterior margin of head usually arcuate; ventral 

sclerite of penis at least twice as long as wide 116 


Figs 121-122 Dorsal view of male: 
edwardsi; 122- Psephenus texanus. 

121- Eubrianax 

116 (115) Maxillary palp about half as long as antenna; ventral 

sclerite of penis emarginate at base (Fig. 124); 
about 4-5.3 mm long, 1.7-3.1 mm wide: Psephenus hervioki 
Maxillary palp about two-thirds to three-fourths as 
long as antenna; ventral sclerite of penis arcuate 
at base 117 

117 (116) Coloration uniformly dark; maxillary palp about two- 

thirds as long as antenna; tarsal claws toothed at 
base; aedeagus with ventral sclerite of penis slender, 
parameres subparallel in dorsal aspect (Figs 125, 
126); about 3.5-5 mm long, 1.6-3 mm wide: 

Psephenus haldemani 
Head and pronotum black, elytra brown, epipleura, 

bases of legs and other parts testaceous; maxillary 

palp about three-quarters as long as antenna; tarsal 

claws not appreciably toothed at base; aedeagus with 

ventral sclerite of penis relatively broad, parameres 

with lateral margins tapering distally from near 

middle (Figs 127, 128); male about 3.2 mm long, 1.6 

mm wide: Psephenus murvoshi 

Figs 123-128 Aedeagus of Psephenus species: 123- P. texanus^ ventral 
aspect with sclerite stippled; 124- P. herriaki, ventral aspect with 
sclerite stippled; 125- P. haldemani, ventral aspect with sclerite 
stippled; 126- P. haldemani, dorsal aspect; 127- P. murvoshi, ventral 
aspect with sclerite stippled; 128- P. murvoshi, dorsal aspect. 


118 (5) Mandibles prominent, acutely margined above (margin 

may be obscured by pubescence), rectangularly flexed 
at tip; head not retracted, moderately deflexed; 
pronotum acutely margined; black with cinerous 
pubescence; 14-22 mm long (Fig. 131): 

Stenocolus sautellaris 
Mandibles not prominent, arcuate at tip, not acutely 

margined above; head strongly deflexed 119 

119 (118) Antennae serrate in female, pectinate in male; middle 

coxae twice as widely separated as anterior coxae; 
margin of pronotum obtusely rounded; presternum short 
in front of coxae; black; 10 mm long (Fig. 129): 

Anohycteis velutina 
Antennae slender; middle coxae no more widely 

separated than anterior coxae; pronotum obtusely 
margined; presternum moderately long before coxae; 
elongate oval; black; 5-6 mm long (rare) (Fig. 130): 

Anchy tarsus biaotor 



Figs 129-131 Dorsal view of adult: 129- Anohycteis velutina male, plus 
antenna of female (from Horn) ; 130- Anchytarsus substriatus female 
(from Champion); 131- Stenocolus scutellaris (from Horn). 





1 Broadly ovoid in shape and very much flattened; lateral 

margins of each segment greatly expanded, the head com- 
pletely concealed from a dorsal view by the expanded 
anterior pronotal margin (water pennies) . . . PSEPHENIDAE ... 33 
Less broad and flat, usually slender with a round or 

triangular cross section; head exposed from dorsal view .... 2 

2 (1) Ninth abdominal segment with a movable ventral operculum 

closing a caudal chamber (Fig . 13) 3 

Ninth abdominal segment without an operculum. .PTILODACTYLIDAE. . 7 

3 (2) Body cylindrical, with abdominal sternites and pleurites 

greatly reduced, the tergites almost forming complete 
rings on first 5 segments and forming complete ones on 
segments 6-9; without retractile gills; abdominal spir- 
acles lateral on segments 1-7 and dorsal on segment 8 

(Unlikely to be found in our streams.) DRYOPIDAE 5 

Body usually not cylindrical; abdominal sternites not 
greatly reduced on anterior segments; with retractile 
filamentous caudal gills emerging from caudal chamber 4 

4 (3) Operculum with a pair of internally attached hooks (Fig. 13)... 9 

Operculum without hooks, but with a flat, movable, dorsal 
sclerite attached to each lateral margin; thoracic seg- 
ments and first 8 abdominal segments each with a 
dorsolateral flattened projection bearing many hairy 
filaments (Fig. 132): CHELONARIIDAE: ChelonaHion 

Figs 132-133 Left lateral aspect of larva: 132- Chelonariim sp. 
(from Boving § Craighead); 133- Dryops sp. (from Bertrand) . 


5 (3) 

6 (5) 

Operculum with 2 toothlike tubercles on posterior margin; 
sides of tergites transversely grooved; ninth abdominal 
segment flattened dorsal ly and emarginate at apex: Helichus 

Operculum without tubercles; tergites not transversely 

grooved; ninth abdominal segment convex dorsally 6 

Tergites with anterior margins smooth; gular sutures 
present (Fig. 133) : 

Tergites (except pronotum) with numerous longitudinal 
carinae arising near each anterior margin; gular 
sutures obliterated, with 2 pairs of setae near where 


sutures would be: 


7 (2) Abdominal segments 1-7 each with 2 ventral tufts of 
filamentous gills; submentum not divided; ninth 
abdominal segment without prehensile appendages 
bearing hooks (Fig. 135): Stenooolus 
Abdominal segments 1-7 without gill tufts; submentum 
divided longitudinally into 3 parts; anal region of 
ninth abdominal segment with 2 curved prehensile 
appendages covered with short spines 8 

Figs 134-135 Larva: 134- Anahytarsus biooloT^ left lateral 
aspect (from Bertrand) ; 135- Stenooolus soutellarisl ^ ventral 
aspect (from Boving S Craighead) . 

8 (7) Ninth abdominal segment with numerous fingerlike anal gills; 

apex without projection (Fig. 134) Anohytarsus 

Ninth abdominal segment with 3 median anal gills and 1 
gill lateral to each prehensile appendage; dorsal, 
flattened apex of ninth segment with small raised 
projection: Anohyoteis 


9 (4) Abdomen with pleurites on at least the first 6 segments; 
ventral surface of thorax sclerotized, usually with 
sternites; thoracic pleurites often divided into 2 
or 3 parts; apex of ninth abdominal segment typically 

emarginate ELMIDAE 10 

Abdomen with pleurites present on only first 4 segments; 
with erect hairs along medial margin of each narrow, 
undivided thoracic pleurite; thoracic sternites 
membranous or absent; apex of ninth abdominal segment 
evenly rounded; each eyespot with 5 ocelli and with 
another ventral ocellus below base of antenna; body 
robust; head almost as wide as thorax, but usually re- 
tracted within it (Figs 136, 137, 138): 


(Larvae of the other genera are unknown; they are probably 
not aquatic.) 


Figs 136-138 Larva of Lutroohus luteus: 136- dorsal 
aspect; 137- ventral aspect; 138- lateral aspect. 

10 (9) Abdomen with pleura on first 8 segments 11 

Abdomen with pleura on first 6 or 7 segments. , .ELMINI 16 

11 (10) Body rather broad, lateral margins expanded. .. .LARIN I 12 

Body slender, elongate, cylindrical or hemicylindrical 

ELMINI, in part 13 

12 (11) With coarse, prominent spines along lateral margins; 

dorsal surface ridged on each side; last segment rather 
square-sided and flat dorsally; procoxal cavities 
open behind; up to 16 mm long (Figs 139, 140): Lara 
Without marginal spines; body quite flattened and with 
rather smooth surface; testaceous to brown, somewhat 
translucent; procoxal cavities closed behind (Figs 
141, 142): Phanoaerus 



Figs 139-142 Larva of Lara avara: 139- dorsal aspect; 

140- ventral aspect. Larva of Phanocerus olavioormis: 

141- dorsal aspect; 142- ventral aspect. 

13 (11) Last abdominal segment very long and slender (at least 

4 times as long as wide) ; operculum confined to poster- 
ior third of segment (Figs 143, 144): Duhiraphia 
Last abdominal segment not conspicuously long or 

slender (less than 4 times as long as wide); operculum 

not confined to apical third 14 

14 (13) Head tuberculate, with suberect spines; anterior margin 

of head without a prominent frontal tooth on each side; 
body subcylindrical, yellowish; often more than 8 mm long 
(Figs 145, 146): Narpus 

Head without suberect spines, anterior margin with a 

prominent frontal tooth on each side (Fig. 13) 15 

15 (14) Body cylindrical; pleural sutures extend to basal half 

of ninth abdominal segment; procoxal cavities closed 
behind (Fig. 147); larger, often longer than 6.5 mm 
(Fig. 148): Cylloepus 

Body hemicylindrical; pleural sutures not extending 

onto ninth abdominal segment; procoxal cavities open 
behind; smaller, less than 6.5 mm (Figs 149, ISO) iRhizelmis 

16 (10) Prothorax with a posterior sternum (Fig. 13) , so 

procoxal cavities are closed behind 17 

Prothorax without posterior sternum; procoxal cavities 

open behind 25 




Figs 143-146 Larva of Dubiraphia sp.: 143- dorsal aspect; 
144- ventral aspect. Larva of Narpus aonaolor: 145- dorsal 
aspect; 146- ventral aspect. 




Figs 147-150 Larva: 147- Cylloepus sp., ventral aspect of 
thoracic and first abdominal segment (from Hinton) ; 
148- C. montanus , dorsal aspect (from Bertrand) . Larva of 
Rhizelmis nigra: 149- dorsal aspect; 150- ventral aspect. 

17 (16) Posterolateral margins of abdominal segments 1-8 

produced into spine- like processes; body rather 
robust (Figs 151, 152): Anoyronyx 

Margins of abdominal segments not thus produced; 

body elongate 18 


18 (17) Dorsum of all but last segment bearing spatulate tuber- 
cles or short spines arranged in about 10 conspicuous 
longitudinal or diagonal rows; last segment with a 
mid-dorsal longitudinal ridge and lateral margins 
bearing spatulate tubercles (Figs 153, 154, 155): Hetevelmis 
Dorsum without such spiny tubercles, although there 

may be rows of small, flat tubercles 19 


Figs 151-155 Larva of Anoyronyx variegata: 151- dorsal aspect; 
152- ventral aspect. Larva of Hetevelmis vulnerata: 153- dorsal 
aspect; 154- lateral aspect; 155- ventral aspect. 

19 (18) Anterior margin of head on each side with a distinct 

frontal tooth (Fig . 13) 22 

Anterior margin of head without distinct frontal tooth 20 

20 (19) Dorsum with relatively conspicuous, flattened tubercles 

often arranged in longitudinal rows; abdominal tergites 
often with mid-dorsal pale spots; last segment with a 

weak mid-dorsal longitudinal ridge 21 

Tubercles of dorsum inconspicuous, not arranged in longitu- 
dinal rows; without mid-dorsal pale spots; last segment 
convex dorsally, without median ridge (Figs 159, 160) : 


21 (20) Last abdominal segment conspicuously long and slender (3 

times longer than wide) ; mid-dorsal spots widest near 
middle of each segment; dorsal tubercles not arranged in 
parallel longitudinal rows: Hexaaylloepus 

Last segment not unusually long or slender; mid-dorsal spots 
widest near posterior of segments; dorsal tubercles 
partially arranged in parallel longitudinal rows (Figs 
156-158) : Miorocylloepus 


Figs 156-160 Larva of Miarocylloepus pusillus: 156- dorsal aspect; 
157- ventral aspect; 158- lateral aspect. Larva of Neoelmis sp.: 
159- dorsal aspect; 160- ventral aspect. 

22 (19) Tergite of last abdominal segment with prominent median 
and sublateral longitudinal carinate ridges (in cross 
section, the segment would be pentagonal) (Figs 161, 
162) : Neoaylloepus 
Dorsum of last abdominal segment not carinate or prom- 
inently ridged 23 


Figs 161-164 Larva of Neoaylloepus boeseli: 161- dorsal aspect; 
162- ventral aspect. Larva of Ordobrevta nubifera: 163- dorsal 
aspect; 164- ventral aspect. 


23 (22) Second segment of antenna more than twice as long as 

first; prosternum with anterior suture obliterated; 
no suture extending from procoxal cavity to lateral 
margin of pronotum (Figs 163, 164): Ordobrevia 

Second segment of antenna less than twice as long as first; 
prosternum with anterior median suture; suture from pro- 
coxal cavity to lateral margin may or may not be visible. 24 

24 (23) Suture from procoxal cavity to lateral margin distinct; 

large and rather flattened, commonly well over 1 mm 
wide; our species usually relatively smooth, black, 
and rather shiny (Figs 165, 166) : Elsianus 

Suture from procoxal cavity to lateral margin indistinct 
or absent; body more convex and elongate, smaller, not 
more than about 1 mm wide; cuticle more granular in ap- 
pearance, from pale tan to dark brown, not shiny (Figs 
167, 168) : Stenelmis 

Figs 165-168 Larva of Elsianus texanus: 165- dorsal aspect; 
166- ventral aspect. Larva of Stenelmis sp.: 167- dorsal aspect; 
168- ventral aspect. 

25 (16) Postpleurite composed of 1 part (Fig. 13) 26 

Postpleurite composed of 2 parts (Fig. 177) 27 

26 (25) Body robust, broad, subtriangular in cross section; with 

spatulate spines along lateral margins and mid-dorsal 
line (Figs 169, 170): Ampumixis 

Body long and slender, hemicylindrical; without prominent 

clusters of spines (Figs 171, 172): Cleptelmis 

27 (25) Mesopleuron composed of 1 part (Fig. 177) 
Mesopleuron composed of 2 parts (Fig. 179) 



Figs 169-172 Larva of Ampumixis dispar : 169- dorsal aspect; 
170- ventral aspect. Larva of Cleptelmis sp.: 171- dorsal 
aspect; 172- ventral aspect. 



Figs 173-177 Larva of Promoresia tardella: 173- dorsal aspect; 
174- ventral aspect; 175- lateral aspect. Larva of Optioservus 
sp.: 176- dorsal aspect; 177- ventral aspect. 

28 (27) 

Dorsum of each segment with median and sub- lateral 

humps (Figs 173, 174, 175): 

(last segment strongly humped in P. elegans , 

feebly humped in P. tccrdella) 
Dorsum without such humps (Figs 176, 177) : 



29 (27) 

Abdominal segments 1-6 with pleura; last segment with 
2 long, acute, narrowly separated apical processes 
(Figs 178, 179) : Maaronyohus 

Abdominal segments 1-7 with pleura 30 


30 (29) Body long, slender, and hemicylindrical; apex of last 

segment rather deeply emarginate, the angles produced 
and acute (Figs 180, 181) Zaitzevia 
Body usually less elongate, subtriangular in cross section; 
apex of last segment shal lowly emarginate, angles less 
acute 31 

Figs 178-181 Larva of Maorony chus glahratus: 178- dorsal aspect; 
179- ventral aspect. Larva of Zaitzevia parvula: 180- dorsal 
aspect; 181- ventral aspect. 

31 (30) Abdominal segments with mid-dorsal humps which are es- 

pecially prominent toward the rear, each hump bearing 
conspicuous scale-like hairs (Fig. 184); dorsum of 
each thoracic segment with 2 longitudinal dark spots 
on each side (Figs 182-184) : Gonielmis 
Abdominal segments without mid-dorsal humps; thorax with- 
out dark markings 32 

32 (31) Western; tubercles of dorsum relatively dense, separated 

by less than their own widths, crowded along posterior 
margins of segments; mesothorax with anterior portion 
of pleuron much smaller than posterior portion; mature 
larva 4-5 mm long (Figs 185, 186): Heterlirmius 

Eastern; tubercles of dorsum sparse, separated by more 
than their own widths except along mid-dorsal line, 
marginal tubercles separated by their own widths; 
mesothorax with anterior portion of pleuron subequal 
to posterior portion; mature larva not over 3 mm 
long (Figs 187, 188): Oulirmius 


Figs 182-184 Larva of Gonielmis dietviahi: 182- dorsal 
aspect; 183- ventral aspect; 184- lateral aspect. 

^M i^--^ ms-r 


Figs 185-188 Larva of Heterlirmius corpulentus : 185- dorsal 
aspect; 186- ventral aspect. Larva of Oulimnius latius cuius : 
187- dorsal aspect; 188- ventral aspect. 

33 (1) Ninth abdominal segment with a ventral operculum 

closing a caudal chamber containing 3 tufts of re- 
tractile filamentous gills; without gills on other 
parts of abdomen; expanded lateral portions of 

abdominal segments separated EUBRIINAE 

Ninth abdominal segment without ventral operculum; with 
pairs of ventral tufts of filamentous gills on 4 or 5 
abdominal segments; expanded lateral portions of ab- 
dominal segments fitting tightly together at margin... 





Figs 189-190 Larva of Acneus quadrimaoulatus : 189- dorsal 
aspect; 190- ventral aspect. 


Figs 191-194 Larva of Dioranopselaphus sp. : 191- dorsal aspect; 
192- ventral aspect. Larva of Ectopria nervosa: 193- dorsal aspect; 
194- ventral aspect. 

Figs 195-198 Larva of Eubrianax edwardsi: 195- dorsal aspect; 

196- ventral aspect. Larva of Psephenus texanus: 197- dorsal aspect; 

198- ventral aspect. 


34 (33) Apex of ninth abdominal segment narrowly emarginate 

(i.e., with a distinct notch) (Figs 189, 190): Acneus 
Apex of ninth segment truncate or broadly arcuate 35 

35 (34) Ninth abdominal segment not rectangular, the sides 

expanding from base toward broadly arcuate apex; 
lateral expansions of eighth segment short, not 
forming part of lateral margin of body outline 
(Figs 191, 192): Dicrcmopselaphus 

Ninth abdominal segment almost rectangular; lateral 
expansions of eighth segment forming part of margin 
of body outline (Figs 193, 194) : Eatopria 

36 (33) Eighth abdominal segment with lateral expansions; 

abdomen with 4 pairs of gills (Figs 195, 196): Eubrianax 
Eighth abdominal segment without lateral expansions; 

abdomen with 5 pairs of gills (Figs 197, 198): Psephenus 



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1940. A monographic revision of the Mexican water beetles of the 

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aoaessory stria -- a short stria which usually fuses with another stria 
near the base of the elytron (Figs 25, 63) . 

aedeagus -- male genitalia (Fig. 10) . 

alutaaeous -- covered with minute cracks or wrinkles, like the human 

angle -- corner (e.g., apical angle of pronotum of humeral angle or 
elytron as in Fig. 1). 

apex (adj., apical) -- that part of a joint or segment farthest from the 
base by which it is attached; the apex of the thorax is anterior, that 
of the abdomen posterior. 

arouate -- arched, bow- like, rounded. 

basal piece -- that part of the aedeagus to which the penis and parameres 
are attached (Fig. 10). 

base (adj., basal) -- that part of a joint nearest to the main body; 
the base of the thorax is the posterior or hind portion, that of the 
abdomen being the anterior or front portion. 

bimaeulate -- bearing two spots (maculae) . 

carina — an elevated ridge or keel (Figs 1, 4). 

carinate -- exhibiting one or more carinae. 

cinereous -- ashy gray in color. 

clypeus -- that part of the head below the frons to which the labrum is 
attached (Figs 2,3). 

coxa -- the basal segment or joint of the leg (Fig. 2). 

crenate -- scalloped with small, blunt, rounded teeth (Fig. 1). 

arenulate -- with small, evenly rounded scallops. 

decimbent -- bending downward (as decumbent hairs in contrast with erect 
ones) . 

decujrved -- bowed or curved downward. 

disc or disk -- the central upper surface (Fig. 1). 


dorsum -- the dorsal or upper surface; opposite of venter. 

elytra (plural of elytron) -- the leathery or sclerotized anterior wings 
which, at rest, cover the hind or flight wings, meeting in a straight 
line down the middle of the dorsum. 

elytral interval -- the region between two adjacent elytral striae; the 
intervals are counted from the center, the first being the sutural interval 
(Fig.l) or that between the midline and the first stria. 

elytral suture -- the mid-dorsal line where the elytra meet in repose. 

emarginate -- notched, indented, hollowed out, curved inward. 

epipleuron -- the deflexed or bent-under portion of the elytron just be- 
low the edge (Figs 2-4) . 

exserted ooxa -- a protruding coxa; one that juts outward. 

femur (plural, femora) -- that segment of the leg between the trochanter 
and the tibia (Fig. 2), sometimes the only part of the leg visible from 
above . 

filiform -- thread-like; slender and of equal diameter; the joints of a 
filiform antenna are relatively uniform and shaped like elongate beads. 

flabellate -- fan-shaped (Fig. 118). 

fovea -- a pit or deep depression. 

fuscous -- dark brown; reddish black. 

genitalia -- the genital organs collectively (Figs 10, 11) . 

glabrous -- smooth and bare. 

gulajc suture -- line of division between the gula (Fig. 7) and the gena 
lateral to it. 

hemistemite -- basal portion (coxite) of female genitalia (Fig. 11), 
sometimes adapted for oviposition. 

humerus -- the basal exterior angle of the elytron (Figs 1, 2). 

hydrofuge pubesaenae -- tomentum; water-repellent fuzz. 

hypomeron -- the deflexed or bent-under portion of the pronotum beneath 
the lateral margin or edge (Figs 2, 3); elytral hypomeron = epipleuron. 

immaculate -- without spots or blotches. 


labial palp -- jointed lateral appendage of the labium (Figs 2, 7, 15). 

labium -- lower lip formed from fused second maxillae (Figs 2, 7, 13, 15). 

labrum -- upper lip, attached basal ly to clypeus and covering bases of 
mandibles (Figs 2, 3) . 

lamellate antenna -- one with a number of terminal segments that are 
flattened and usually appressible like the pages of a book (Fig. 92). 

lotia -- with moving water, either wave-washed or flowing. 

maculate -- with spots (maculae) . 

mandible -- lateral jaw (Figs 2, 3, 5). 

maxilla -- lateral mouth part between mandible and labium (Figs 6, 13, 

maxillary palp -- jointed appendage of maxilla (Figs 2, 3, 6, 14); 
often the most conspicuous mouthpart on the intact specimen. 

mesopleuron -- pleuron of mesothorax. 

mesostenmum -- sternum of mesothorax (Figs 2, 13) . 

mesothorax -- middle segment of thorax; to it are attached the second 
or middle pair of legs and, in adults, the elytra. 

metapleuron -- pleuron of metathorax. 

metastemum -- sternum of metathorax (Figs 2, 13) . 

metathorax -- third segment of thorax; to it are attached the third 
or hind pair of legs and, in adults, the flight wings. 

moniliform antenna -- one with joints or segments like rather uniform 
globular beads. 

ocellus (plural, ocelli') --a simple eye or eyespot. 

oahreous or ochraceous -- brownish yellow. 

operculum -- trapdoor- like ventral cover of gill chamber on last ad- 
dominal segment of larva (Fig. 13). 

ovipositor -- sclerotized parts of female genitalia (usually hemistern- 
ites) adapted for insertion of eggs into the substrate (e.g., in Helichus, 
Figs 95, 101, 102). 

paramere -- lateral lobe of male genitalia, attached to basal piece and 
enclosing penis (Fig. 10). 


pectinate antenna -- one in which a number of segments are enlarged into 
long tooth- like projections so that the antenna resembles a comb or a 
garden rake (Fig. 121) . 

penis -- median lobe of male genitalia, attached to basal piece and flanked 
or enclosed by the paired parameres (Fig. 10) , 

pile -- pubescence; fuzz; short, dense hairs. 

plastron -- gaseous film maintained under water by means of small, close- 
set, hydrofuge hairs covering parts of the body surface. 

pleurite -- a sclerite covering part or all of a pleuron (Fig. 13). 

pleuron (plural, pleio'a') -- the lateral region of a body segment between 
tergum and sternum. 

postpleurite -- the pleurite of the prothorax behind the coxa (Fig. 13). 

proGoxa -- the coxa of a front leg (Fig. 3). 

pronotum -- the dorsal portion of tergum of the prothorax (Figs 1, 3, 12). 

propleuron -- the pleuron of the prothorax, 

prostemal process -- posterior median projection of the presternum 
between the procoxae (Fig. 2). 

pvostemum -- sternum of the prothorax (Figs 2, 3, 13). 

prothorax -- first segment of thorax, to which head is attached and into 
which the head may be partially or entirely withdrawn; this segment also 
bears the front pair of legs. 

pubescence -- fuzz; hairs. 

puncta, punctation -- small punctures or pits in the surface; rows of 
such punctures form the striae of the elytra. 

recia>ved -- bent or curved upward. 

riparian -- shore-dwelling; occurring at or near the margin of the water. 

rufous -- reddish. 

sclerite --a hardened piece or section of the exoskeleton. 

sclerotised -- hardened. 

sautellum -- the wedge-shaped median dorsal sclerite between the basal 
portions of the elytra (Fig. 1). 


sericeous -- silky; downy. 

serrate -- saw-toothed (e.g., serrate elytral margin as in Fig. 1 or 
serrate antenna as in Fig. 120). 

stemite -- a sclerite of the sternum (Figs 1-4, 13). 

sternum -- the ventral part of a body segment. 

stria -- a row of punctures forming a longitudinal line (Fig. 1). 

stylus -- sensory projection of the female genitalia attached to hemi- 
sternite (Fig. 11) . 

sub- (prefix) -- almost; nearly; slightly; close to; just below, 
(e.g., subequal; subquadrate.) 

sublateral carina -- a lateral longitudinal carina parallelling the 
lateral margin (Figs 1, 3). 

submentum -- the basal sclerite of the labium by which the labium is 
attached to the gula of the head (Fig. 7). 

sulcus (plural, sulci) -- a groove or furrow. 

sutural interval -- the first or median elytral interval (Fig. 1). 

sutural vitta — a vitta or stripe bordering the elytral suture (Figs 
81, 82). 

suture -- a seam or impressed line between two contiguous sclerites; 
the median line of juncture of the elytra (Figs 12, 13). 

tarsus -- the foot; the distal part of the leg attached at the apex of 
the tibia, consisting typically of five joints or segments and bearing 
the tarsal claws (Fig. 2). 

tergite -- a sclerite of the tergum (the dorsal part of a segment) 
(Figs 1, 12, 13). 

testaceous -- yellow; brownish yellow. 

thorax -- the body region between the head and the abdomen; the thorax 
bears the legs and, in adults, the wings. 

tibia -- the joint or segment of the leg between the femur and the 
tarsus (Fig. 2) . 

tomentum -- a dense patch of hairs, either prominent, as on the tibia 
(Fig. 2), or closely appressed to the surface and providing a plastron 
on various body sclerites. 


tPansverse coxa --an elongate coxa extending transversely like the hind 
coxa of Fig. 2. 

travertine -- a rather porous calcareous stone which forms on the sub- 
strate in falls and rapids of streams with a very high calcium content. 

trodhantin -- a small piece or joint on the outer side of the coxa (well 
separated from the trochanter) which may be exposed or may be hidden 
beneath the pronotum or presternum . 

truncate -- cut off squarely or abruptly at the tip. 

tubercle -- a small button-like or pimple-like projection of the exo- 

tuberaulate -- bearing tubercles. 

umbone -- an embossed, elevated knob on the humeral angle of an elytron 
(Fig. 1). 

venter -- the ventral surface or under side of the body. 
vitta -- a longitudinal stripe, usually relatively broad. 
vitiate -- striped; bearing vittae. 



dbnormis (Cylloepus) , 14,40 
AoneuSj 23,51,67 

ovegonensis, 23,51 

quadrimaculatus i 23,51 

addenda ( Cleptelmis) ^ 14,35 
ampliatus (Optioservus) ^ 17,45 
Ampumixisj 14,62 

dispar, 14,35 

AnahyateiSy 24,56 

velutina^ 24,54 

Anchytarsus , 24,56 

hioolovy 24,54 

AncyronyXj 4,14,59 

variegata, I A ,21 

angustus (Naj^us), 16,35 
antennalis (Stenelmis) ^ 20,32 
arizonensis (Dvyops) , 21,46 
arisonicus (Lutrochus) ^ 22,50 

(Narpus), 17,36 

AtraatelmiSj 14 

wawona, 14,35 

avara amplipennis (Lara), 13,26 

avara (Lara) , 13,26 

basalis (Hetiohus) , 21,48 
beameri ( Stenelmis) , 20,30 
hioarinata (Stenelmis) , 20,31 
bicolor (Anchy tarsus) J 24,54 
bivittata (Dubiraphia) , 14,36 
boeseli (Neocylloepus) , 17,38 
browni (Miorocylloepus) , 16,41 
brunnesaens (Dubiraphia.) , 15,37 
Byrrhoidea, 1 
caesa (Neoelmis) , 17,38 
calida oalida (Stenelmis) , 20,28 

moapa (Stenelmis) , 20,28 

oanus (Optioservus) , 17,45 
Cephalobyrrhinae, 23, 50 
Chelonariidae, 1,2,5,13,55 
Che lonarium, 2,13,55 

leoontei, 13,25 

alavicomis (Phanooerus) , 13,26 
Cleptelmis, 14,35,62 

addenda i 14,35 

omata, 14,35 

oonoinna (Stenelmis) , 20,30 
oonoolor (Narpus), 17,36 

aonfluentus (Heliohus) , 22,46 
aonvexuta (Stenelmis) , 20,34 
aorpulentus ( Heterlimnius) , 15,43 
crenata (Stenelmis) , 20,30 
cryophilus (Optioservus), 17,44 
Cylloepus, 14,40,58 

abnormis, 14,40 

parkerij 14,40 

sexualiSj 14 

Dascillidae, 1 
Dascilloidea, 1 
decorata (Stenelmis) , 20,33 
Diaranopselaphus, 23,67 

variegatuSj 23,52 

dietriahi (Gonielmis), 15,42 
dispar (Ampumixis), 14,35 
divergens (Optioservus) , 17,44 
douglasensis (Stenelmis) , 20,31 
Dryopidae, 1,3,21,25,55 
Dryopoidea, 1 
Dryops, 3,4,21,56 

arisonensiSj 21,46 

viennensiSj 21 

Dubiraphia^ 4,14,35,58 

bivittata, 14,36 

brunnesaens, 15,37 

giulianii, 15,37 

quadrinotata, 15,37 

vittata, 15,37 

Eotopria, 2,4,23,67 

nervosa, 23,52 

edwardsi (Eubrianax) , 24,52 
elegans (Promoresia) , 19,42 
Elmidae, 1,13,25,57 
Elmini, 1,14,26,57 
Elminthidae, 13 
Elsianus, 15,37,62 

moestus, 15,38 

shoemakei, 15,38 

texanus, 15,38 

Eubrianacinae, 24 
Eubrianax, 2,4,24,67 

edwardsi, 24,52 

Eubriinae, 2,5,23,51,65 

Eurypogonidae, 1 

exigua (Stenelmis), 20,30 


exilis (Stenelmis) 3 20,31 
fastiditus (Optioservus) 3 17,45 
fastigiatus (Helichus) y 22,48 
ferrugineus (Hexaoy Z loepus ) ^ 16,39 
fusoata (Stenelmis) , 20,32 
ge hringi (Lara ) ^ 13,26 
gi-ulianii ( Dubiraphia) , 15,37 
glabra (Eeterelmis) , 15,39 
glabratus (Maaronychus) ^ 16,27 
Gonielmis, 4,15,64 

dietriohi, 15,42 

gross a (Stenelmis), 20,31 
haldemani (Psephenus) , 24,53 
HeliahuSj 1,3,4,21,46,56 

basaliSj 21,48 

aonfluentus, 22,46 

fastigiatus, 22,48 

immsi, 22,47 

lithophilus , 22,48 

productuSj 22, Al 

striatus foveatus, 22,49 

striatus, 22,49 

suturalis, 22,49 

triangularis, 22,49 

herricki (Psephenus) , 24,53 
Heterelmis, 4,8,15,39,60 

glabra, 15,39 

obesa, 15,39 

vulnerata, 15,39 

Heterlimnius , 15,43,64 

aorpulentus, 15,43 

koebeleij 16,43 

Heteroceridae, 1 
Hexaoylloepus , 16,60 

ferrugineus, 16,39 

humerosa (Stenelmis) , 20,32 
hungerfordi (Stenelmis) , 20,32,33 
immsi (Helichus) , 22,47 
immunis ( Optics ervus ) , 17,44 
knobeli (Stenelmis) , 20,31 
koebelei (Heterlimnius) , 16,43 
Lara, 2,13,26,57 

avara amplipennis, 13,26 

avoj^a, 13,26 

gehringi, 13,26 

Larini, 2,13,26,57 
lateralis (Stenelmis) , 20,30 
laticeps (Lutrochus) , 22,51 
latiusoulus (Oulimnius), 19,41 
leaontei (Chelonarium) , 13,25 
Limnichidae 1,2,22,25,57 

Limnichinae, 22,50 
Limniohus, 2,4,22,50 
lithophilus (Helichus) , 22,48 
luteus (Lutrochus) , 23,51 
Lutrochus, 1,2,4,5,22,50,57 

arisonicus, 22,50 

laticeps, 22,51 

luteus, 23,51 

Macronychus, 4,16,63 

glabratus, 16,27 

markeli (Stenelmis) , 21,34 
mera (Stenelmis) , 21,31 
Microoylloepus , 4,16,40,60 

browni, 16,41 

moapus, 16,41 

fraxinus, 16,41 

moapus, 41 

pusillus, 16,40 

aptus, 16,41 

lodingi, 16,41 

perditus, 13,16,41 

pusillus, 16,41 

similis, 16,41 

thermarum, 16,40 

minutus (Physemus) , 23,50 
mirabilis (Stenelmis) , 21,32 
moapus (Microcylloepus) , 16,41 

fraxinus (Microcylloepus) , 16,41 

moapus (Microcylloepus) , 41 

moestus (Elsianus) , 15,38 
murvoshi (Psephenus) , 24,53 
musgravei (Stenelmis) , 21,33 
Narpus, 16,35,58 

angustus, 16,35 

arizoniaus, 17,36 

Goncolor, 17,36 

Neoaylloepus, 8,10,17,61 

boeseli, 17,38,61 

Neoelmis, 17,60 

caesa, 17,38 

nervosa (Ectopria) , 23,52 
nigra (Rhizelmis) , 20,34 
nubifera (Ordobrevia) , 19,28 
obesa (Heterelmis) , 15,39 
obsGurus (Pelonomus) , 22,46 
Optioservus, 17,43,63 

ampliatus, 18,45 

canus, 17,45 

oryophilus, 17,44 

divergens, 17,44 

fastiditus, 17,45 


Optioservus immunis, 17,44 

ovalis, 17,45 

ozcxrkensis y 13,17,44 

peaosensiSj 18,44 

quadrimaaulatus y 18,45 

sandevsoni, 13,18,44 

seriatuSj 19,45 

trivittatus J 18,19,44 

Ordobvevia, 19,61,62 

nubiferuj 19,28 

oregonensis (Aoneus)^ 23,51 
ornata (Cleptelmis) ^ 14,35 
Oulimnius^ 19,64 

latiusauluSj 19,41 

ovalis (Optioservus) , 17,45 
osarkensis (Optioservus) j 13,17,44 
parkeri (Cylloepus) ^ 14,40 
parva (Stenelmis) , 21,31 
parvula (Zaitzevia) , 21,28 
pecosensis (Optioservus) ^ 8,44 
PelonomuSj 3,22,56 

obscuruSj 22,46 

Phanocerus, 2,4,13,57 

ctavicomis, 13,26 

PhysemuSj 23 

minutus, 23,50 

Polyphaga, 1 

pvoduatus (Heliohus) J 22, Al 

Promoresiaj 19,42,63 

eleganSj 19,42 

tardella, 19,42 

Psephenidae. 1,2,23,26,55 

Psepheninae, 24 

Psephenus, 1,2,4,5,24,52,67 

haldemani^ 24,53, 

herriaki, 24,53 

murvoshiy '24,53 

texanus, 24,52 

Ptilodactylidae, 1,5,24,26,55 
pusillus (Microaylloepus) J 16,40 

aptus (Miarocylloepus) J 16,41 

lodingi (Microcylloepus ) , 16,41 

perditus (Microcylloepus) , 13,16,41 

pusillus (Microoylloepus) J 16,41 

similis (Miarooylloepus) , 16,41 

quadrimaaulata ( Stenelmis ) , 21,33 
quadrimaaulatus (Acneus), 23,51 

(Optioservus) y 18,45 

quadrinotata (Dubiraphia) , 15,37 
RhizelmiSy 20,58 
nigra J 20,34 

Sander soni (Optioservus) ^ 13,18, 


(Stenelmis), 21,30 

SGUteltaris (Ste?ioaolus) , 24,54 
seriatus (Optioservus) , 19,45 
sexlineata (Stenelmis), 21,30 
sexualis (Cylloepus) , 14 
shoemakei (Elsianus) , 15,38 
sinuata (Stenelmis) , 21,33 
Stenelmis, 7,20,28,62 

antennalis, 20,32 

beameri, 20,30 

bieajcinata, 20,31 

catida calida, 20,28 

moapa, 20,28 

Gonoinna, 20,30, 

convexula, 20,34 

crenata, 20,30 

deoorata, 20,33 

douglasensisy 20,31 

exigua, 20,30 

exilis, 20,31 

fusaata, 20,32 

grossa, 20,31 

humerosa, 20,32 

hunger fordi, 20,32,33 

knobeli, 20,31 

lateralis, 20,30 

markeli, 21,34 

mera, 21,31 

miraJbilis, 21,32 

musgravei, 21,33 

parva, 21,31 

quadrirnaaulata, 21,33 

sandersoni, 21,30 

sexlineata, 21,30 

sinuata, 21,33 

vittipennis, 21,33 

Stenobolus, 24,56 

soutellaris, 24,54 

striatus foveatus (Helichus) , 22, 


striatus (Helichus), 22,49 

suturalis (Helichus) , 22,49 
tardella (Promoresia) , 19,42 
texanus (Elsianus), 15,38 

(Psephenus), 24,52 

thermae (Zaitzevia) , 21,28 
thermarum (Microoylloepus) , 16, 

Throscinus, 23 


triangularis (Heliohus) ^ 22,49 vittipennis (Stenelmis) , 21,32 

trivittatus (Optioservus) , 18,19,44 vulnevata (Hetevelmis) , 15,39 

variegata (Anayronyx) , 14,27 wawona (Atvaotelmis) , 14,35 

variegatus (Dicranopselaphus) , 23,52 Zaitzevia, 21,28,64 

velutina (Anahyoteis) , 24,52 parvula^ 21,28 

viennensis (Dry ops), 21 thermae , 21,28 

vittata (Dubiraphia) J 15,37 




1. Report No. 

NO. 6 Aquatic Dryopoid Beetles (Coleoptera) of the United 

7. Author(s) 

Brown, H. P. 

9. Organization department of Zoology 

The University of Oklahoma 
Norman, Oklahoma 

12. Sponsoring Organization 
15. Supplementary Notes 

3. Accession No. 


5. Report Date 


S. Performing Organization 
Report No. 

10. Project No. 

18050 ELD 

11. Contract/Grant No. 

IS. Type of Report and 
Period Covered 

16. Abstract An illustrated key is given for all known species of adult dryopoid 
beetles of the United States which have aquatic stages and might be 
useful as indicators of water quality. A key is also given to the 
genera of larvae. For each species the known habitat and range are 
given. Life histories are briefly outlined and methods for collection, 
preservation, storage and identification are suggested. Two new 
species, Optioservus ozarkensis Collier and Optioservus sandersoni 
Collier, are described. The genera included in the keys are: 
C\\elonaTii6.a.e --Chelonarium; Elmidae--Tribe LariniiLarCj Phanoaerus; 
Tribe Elmini: Ampumixis, AncyronyXj Atraatetmis , Cleptelmis, Cylloepus, 
Dubivaphia, Elsianus, Gonielmis, EeteveVnis, HeterlimniuSj Eexaaylloepus ^ 
Maaronyohus, MioroaylZoepuSj Narpus, Neoayltoepus^ Heoelmis, 
OptioservuSj Ordobrevia, Oulimnius, Promoresia, Rhizetmis, Stenelmis, 
Zaitzevia; Dryopidae--£'rn/opSj Reliahus, Pelonomus; Limnichidae-- 
Limnichinae: Lirmiahus, Lutrochus, Physemus; Cephalobyrrhinae: 
Throsoinus; Psephenidae--Eubriinae: Aaneus, Diaranopselaphus, Eatopria; 
Eubrianacinae: Eubrianax; Psepheninae: Psephenus; Ptilodactylidae-- 
Anahycteis, Anohy tarsus , Stenoaolus. The bibliography includes 
selected references in addition to the literature cited. 

/7a. Descriptors *Aquatic fauna, *Insects, *Water beetles, *United States, Preservation, 

/7fi. /den(;^ers*i(jentification Manual, *lllustrated Key, *Coleoptera, *Dryopoidea, 

nc.COWRR Field & Group 


IS. Availability 

19. Security Class. 

20. Security Class. 

21. No. of 

22. Price 

Send To: 


Abstractor Harley p. Brown 

{institution The University of Oklahoma 

WRSIC 102 (REV JUNE 1971) 

o U. S. GOVERNMENT PRINTING OFFICE : 1972 O - 467-252